Dual anthrax-plague vaccines that can protect against two tier-1 bioterror pathogens, bacillus anthracis and yersinia pestis

ABSTRACT

Bivalent immunogenic compositions against anthrax and plague are disclosed herein. One bivalent immunogenic composition comprises a triple fusion protein containing three antigens, F1 and V from Yersinia pestis and PA antigen from Bacillus anthracis fused in-frame and retaining structural and functional integrity of all three antigens. Another bivalent immunogenic composition comprises bacteriophage nanoparticles arrayed with these three antigens on the capsid surface of the bacteriophage nanoparticles. These bivalent immunogenic compositions are able to elicit robust immune response in a subject administered said the bivalent immunogenic compositions and provide protection to the subject against sequential or simultaneous challenge with both anthrax and plague pathogens.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application priority to U.S. Provisional Patent Application No. 62/456,825, entitled filed Feb. 9, 2017. The entire contents and disclosures of this patent application is incorporated herein by reference in its entirety.

This application makes reference to the following applications: U.S. Pat. No. 8,148,130, entitled “T4 Bacteriophage Bound to a Substrate,” filed Feb. 29, 2008, issued Apr. 3, 2012, which claims the priority of U.S. Provisional patent Application No. 60/904,168 entitled “Liposome-Bacteriophage Complex As Vaccine Adjuvant,” filed Mar. 1, 2007; U.S. Pat. No. 8,685,694, entitled “Methods and Compositions Comprising Bacteriophage Nanoparticles,” filed Dec. 17, 2004, issued Apr. 1, 2014, which claims priority to U.S. Provisional Application Ser. No. 60/530,527 filed Dec. 17, 2003; U.S. Pat. No. 8,802,418, entitled “Protein and Nucleic Acid Delivery Vehicles, Components and Mechanisms Thereof,” filed Apr. 8, 2011, issued Aug. 12, 2014, claims benefit of priority to U.S. Provisional Patent Application No. 61/322,334 entitled “A Promiscuous DNA Packaging Machine from Bacteriophage T4,” filed Apr. 9, 2010; U.S. Pat. No. 9,163,262, entitled “In vitro and in vivo delivery of genes and proteins using the bacteriophage T4 DNA packaging machine,” filed Dec. 4, 2013, issued Oct. 20, 2015, which claims benefit of priority to U.S. Provisional Patent Application No. 61/774,895 filed Mar. 8, 2013, entitled “In Vitro and In Vivo Delivery of Genes and Proteins Using the Bacteriophage T4 DNA Packaging Machine”; U.S. Pat. No. 9,187,765, entitled “In Vitro And in Vivo Delivery of Genes and Proteins Using the Bacteriophage T4 DNA Packaging Machine,” filed Jul. 22, 2014, issued Nov. 17, 2015, which is a divisional of application Ser. No. 14/096,238 filed Dec. 4, 2013, which claims benefit of priority to U.S. Provisional Patent Application No. 61/774,895 filed Mar. 8, 2013, entitled “In Vitro and In Vivo Delivery of Genes and Proteins Using the Bacteriophage T4 DNA Packaging Machine”; U.S. Pat. No. 9,328,145, entitled “Designing a soluble full-length HIV-1 gp41 trimer,” filed Nov. 27, 2013, issued May 3, 2016, which claims benefit of priority to U.S. Provisional Patent Application No. 61/731,147 filed Nov. 29, 2012, entitled “Designing a Soluble Full-Length HIV-1 Gp41 Trimer”; U.S. Pat. No. 9,328,149, entitled “Mutated and bacteriophage T4 nanoparticle arrayed F1-V immunogens from Yersinia pestis as next generation plague vaccines,” filed Jul. 1, 2014, issued May 3, 2016, which claims benefit of priority to U.S. Provisional Patent Application No. 61/845,487 to Rao and Tao, entitled “Mutated and Bacteriophage T4 Nanoparticle Arrayed F1-V Immunogens from Yersinia Pestis as Next Generation Plague Vaccines,” filed Jul. 12, 2013; U.S. Pat. No. 9,365,867, entitled “Protein and Nucleic Acid Delivery Vehicles, Components and Mechanisms Thereof,” filed Mar. 12, 2013, issued Jun. 14, 2016, which is a divisional application of U.S. patent application Ser. No. 13/082,466, filed Apr. 8, 2011, which claims benefit of priority to U.S. Provisional Patent Application No. 61/322,334 entitled “A Promiscuous DNA Packaging Machine from Bacteriophage T4” filed Apr. 9, 2010; U.S. Pat. No. 9,523,101, entitled “Protein and nucleic acid delivery vehicles, components and mechanisms thereof,” filed Jul. 2, 2014, issued Dec. 20, 2016, which claims benefit of priority to U.S. patent application Ser. No. 13/082,466 to Rao, entitled “Protein and Nucleic Acid Delivery Vehicle, Components and Mechanisms Thereof” filed Apr. 8, 2011, now U.S. Pat. No. 8,802,418; and U.S. Provisional Patent Application No. 61/322,334 entitled “A Promiscuous DNA Packaging Machine from Bacteriophage T4,” filed Apr. 9, 2010; U.S. Pat. No. 9,580,477, entitled “Approach to produce HIV-1 GP140 envelope protein trimers,” filed Jul. 23, 2015, issued Feb. 28, 2017, which claims benefit of priority to U.S. Provisional Patent Application No. 62/133,578, entitled “A New Approach to Produce HIV-1 Gp140 Envelope Protein Trimers,” filed Mar. 16, 2015; U.S. Provisional Patent Application No. 62/166,271, entitled “A New Approach to Produce HIV-1 Envelope Trimers: Both Cleavage and Proper Glycosylation are Essential to Generate Authentic Trimers,” filed May 26, 2015; U.S. Pat. No. 9,701,722, entitled “Designing a Soluble Full-Length HIV-1 Gp41 Trimer,” filed Mar. 25, 2016, issued Jul. 11, 2017, which claims benefit of priority to U.S. Provisional Patent Application No. 61/731,147 filed Nov. 29, 2012, entitled “Designing a Soluble Full-Length HIV-1 Gp41 Trimer”; U.S. Pat. No. 9,834,583, entitled “Authentic Trimeric HIV-1 GP140 Envelope Glycoproteins Comprising a Long Linker and Tag,” filed Jul. 23, 2015, issued Dec. 5, 2017, which claims benefit of priority to U.S. Provisional Patent Application No. 62/133,578, entitled “A New Approach to Produce HIV-1 Gp140 Envelope Protein Trimers,” filed Mar. 16, 2015; U.S. Provisional Patent Application No. 62/166,271, entitled “A New Approach To Produce HIV-1 Envelope Trimers: Both Cleavage And Proper Glycosylation Are Essential To Generate Authentic Trimers,” filed May 26, 2015; U.S. Pat. No. 9,850,288, entitled “Method of purifying authentic trimeric HIV-1 envelope glycoproteins comprising a long linker and tag,” filed Jul. 23, 2015, issued Dec. 26, 2017, which claims benefit of priority to U.S. Provisional Patent Application No. 62/133,578, entitled “A New Approach to Produce HIV-1 Gp140 Envelope Protein Trimers,” filed Mar. 16, 2015; U.S. Provisional Patent Application No. 62/166,271, entitled “A New Approach to Produce HIV-1 Envelope Trimers: Both Cleavage and Proper Glycosylation are Essential to Generate Authentic Trimers,” filed May 26, 2015; U.S. patent application Ser. No. 14/806,735, entitled “Approach to Produce HIV-1 Gp140 Envelope Protein Trimers,” filed Jul. 23, 2015, which claims benefit of priority to U.S. Provisional Patent Application No. 62/133,578, entitled “A New Approach to Produce Hiv-1 Gp140 Envelope Protein Trimers,” filed Mar. 16, 2015; U.S. Provisional Patent Application No. 62/166,271, entitled “A New Approach to Produce HIV-1 Envelope Trimers: Both Cleavage and Proper Glycosylation are Essential to Generate Authentic Trimers,” filed May 26, 2015; U.S. patent application Ser. No. 14/806,751, entitled “Approach to Produce HIV-1 Gp140 Envelope Protein Trimers,” filed Jul. 23, 2015, which claims benefit of priority to U.S. Provisional Patent Application No. 62/133,578, entitled “A New Approach to Produce HIV-1 Gp140 Envelope Protein Trimers,” filed Mar. 16, 2015; and U.S. Provisional Patent Application No. 62/166,271, entitled “A New Approach to Produce HIV-1 Envelope Trimers: Both Cleavage and Proper Glycosylation are Essential to Generate Authentic Trimers,” filed May 26, 2015. The entire disclosure and contents of the above applications are hereby incorporated by reference.

This application further makes reference to the following applications: U.S. Provisional Application No. 60/904,168 filed Mar. 1, 2007; U.S. patent application Ser. No. 12/039,803, filed Feb. 29, 2008; International Application No. PCT/US2008/055422 filed Feb. 29, 2008; U.S. patent application Ser. No. 11/015,294, filed Dec. 17, 2014; U.S. Provisional Application No. 61/322,334, filed Apr. 9, 2010; International Application No. PCT/IB2011/015133, filed Apr. 8, 2011; U.S. Provisional Application No. 62/133,578, filed Mar. 16, 2015; U.S. patent application Ser. No. 14/806,727, filed Jul. 23, 2015; International Application No. PCT/IB2016/054176, filed Jul. 13, 2016; U.S. patent application Ser. No. 14/806,735, filed Jul. 23, 2015; U.S. patent application Ser. No. 14/806,739, filed Jul. 23, 2015; U.S. patent application Ser. No. 14/806,742, filed Jul. 23, 2015; U.S. patent application Ser. No. 14/806,751, filed Jul. 23, 2015; U.S. Provisional Application No. 62/166,271; filed May 26, 2015; International Application No. PCT/IB2016/054207, filed Jul. 14, 2016; International Application No. PCT/IB2016/054250, filed Jul. 15, 2016; International Application No. PCT/IB2016/054260, filed Jul. 18, 2016; International Application No. PCT/IB2016/054292, filed Jul. 19, 2016; U.S. Provisional Application No. 61/731,147 filed Nov. 29, 2012; U.S. patent application Ser. No. 14/091,401, filed Nov. 27, 2013; International Application No. PCT/IB2013/060453, filed Nov. 27, 2013; U.S. patent application Ser. No. 15/080,804, filed Mar. 25, 2016; U.S. Provisional Application No. 61/845,487, filed Jul. 12, 2013; U.S. patent application Ser. No. 14/320,731, filed Jul. 1, 2014; International Application No. PCT/IB2014/063005, filed Jul. 10, 2014; U.S. Provisional Application No. 61/774,895, filed Mar. 8, 2013; U.S. patent application Ser. No. 14/096,238, filed Dec. 4, 2013; International Application No. PCT/IB2014/058716, filed Jan. 31, 2014; and U.S. patent application Ser. No. 14/337,545, filed Jul. 22, 2014. The entire disclosure and contents of the above applications are hereby incorporated by reference.

GOVERNMENT INTEREST STATEMENT

This invention was made with government support under Grant NIH-5R01AI111538 awarded by the National Institutes of Allergy and Infectious Diseases. The government has certain rights in the invention.

STATEMENT REGARDING SEQUENCE LISTING

The Sequence Listing associated with this application is provided in text format in lieu of a paper copy, and is hereby incorporated by reference into the specification. The name of the text file containing the Sequence Listing is 109007-440002_ST25.txt. The text file is 28 KB, was created on Feb. 8, 2018, and is being submitted electronically via EFS-Web, concurrent with the filing of the specification.

BACKGROUND Field of the Invention

The present invention generally relates to vaccines against anthrax and plague pathogens.

Related Art

Bioterrorism remains as one of the biggest challenges to global security and public health. Since the deadly anthrax attacks of 2001 in the United States, Bacillus anthracis and Yersinia pestis, the causative agents of anthrax and plague, respectively, gained notoriety and were listed by the CDC as Tier-1 biothreat agents. Currently, there is no Food and Drug Administration-approved vaccine against either of these threats for mass vaccination to protect general public, let alone a bivalent vaccine.

SUMMARY

According to a first broad aspect, the disclosed invention provides an immunogenic composition comprising a triple fusion protein. The triple fusion protein comprises: a mutated F1 antigen from Yersinia pestis, a V antigen from Yersinia pestis, and a protective antigen (PA) from B. anthracis. The mutated F1 antigen, the V antigen, and the PA are fused in-frame. The triple fusion protein has an immunogenicity of the mutated F1 antigen, an immunogenicity of the V antigen, and an immunogenicity of the PA.

According to a second broad aspect, the disclosed invention provides an immunogenic composition comprising one or more bacteriophage nanoparticles arrayed with one or more Soc fusion proteins on capsid surface of each bacteriophage nanoparticle, wherein the one or more Soc fusion proteins comprises a Soc fused to an antigen selected from the group consisting of a mutated F1 antigen from Yersinia pestis, a V antigen from Yersinia pestis, a protective antigen (PA) from B. anthracis, and combination thereof.

According to a third broad aspect, the disclosed invention provides a method comprising: administering to a subject in need thereof a therapeutically effective amount of an immunogenic composition. The immunogenic composition comprises a triple fusion protein and/or one or more bacteriophage nanoparticles, each bacteriophage nanoparticle being arrayed with one or more Soc fusion proteins on capsid surface of the bacteriophage nanoparticle. The triple fusion protein comprises an in-framed fused mutated F1 antigen from Yersinia pestis, an in-framed fused V antigen from Yersinia pestis, and an in-framed fused protective antigen (PA) from B. anthracis. The one or more Soc fusion proteins comprises a Soc fused to an antigen selected from the group consisting of a mutated F1 antigen from Yersinia pestis, a V antigen from Yersinia pestis, a protective antigen (PA) from B. anthracis, and a combination thereof. The immunogenic composition is able to elicit immune response in the subject against anthrax and plague pathogens.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated herein and constitute part of this specification, illustrate exemplary embodiments of the invention, and, together with the general description given above and the detailed description given below, serve to explain the features of the invention.

FIG. 1A is a schematic illustration of anthrax toxin pathway.

FIG. 1B is a schematic illustration of Y. pestis surface components targeted for vaccine design.

FIG. 2A is a schematic illustrating protective antigen (PA) and F1mutV-PA recombinant constructs according to one embodiment of the present invention.

FIG. 2B is a structural model of F1mutV-PA triple antigen according to one embodiment of the present invention.

FIG. 2C illustrates the binding of F1mutV-PA to PA receptor, CMG2, according to one embodiment of the present invention.

FIG. 2D illustrates furin cleavage of F1mutV-PA according to one embodiment of the present invention.

FIG. 2E illustrates the binding of F1mutV-PA to N-terminal domain of lethal factor (LFn) according to one embodiment of the present invention.

FIGS. 3A, 3B, 3C, and 3D illustrate the display of F1mutV-Soc and Soc-PA on Hoc-Soc-bacteriophage T4 according to one embodiment of the present invention.

FIG. 4A shows vaccine formulations used in various immunized mouse groups according to one embodiment of the present invention.

FIG. 4B illustrates the immunization scheme according to one embodiment of the present invention.

FIG. 4C is a graph illustrating F1V-specific antibody titers according to one embodiment of the present invention.

FIG. 4D is a graph showing PA-specific antibody titers according to one embodiment of the present invention.

FIG. 4E is a graph showing LeTx-neutralizing antibody titers according to one embodiment of the present invention.

FIG. 5A is a graph illustrating F1V-specific IgG1 antibody titers elicited by F1mutV-protective antigen (PA) triple antigen and T4-F1mutV/PA in mice according to one embodiment of the present invention.

FIG. 5B is a graph illustrating F1V-specific IgG2a antibody titers elicited by F1mutV-protective antigen (PA) triple antigen and T4-F1mutV/PA in mice according to one embodiment of the present invention.

FIG. 5C is a graph illustrating PA-specific IgG1 antibody titers elicited by F1mutV-protective antigen (PA) triple antigen and T4-F1mutV/PA in mice according to one embodiment of the present invention.

FIG. 5D is a graph illustrating PA-specific IgG2a antibody titers elicited by F1mutV-protective antigen (PA) triple antigen and T4-F1mutV/PA in mice according to one embodiment of the present invention.

FIG. 6A is a graph illustrating survival of the mice against anthrax toxin and plague sequential challenge according to one embodiment of the present invention.

FIG. 6B is a graph illustrating survival of the mice against anthrax toxin and plague simultaneous challenge according to one embodiment of the present invention.

FIG. 6C are in vivo imaging of infected mice according to one embodiment of the present invention.

FIG. 7A is a table showing vaccine formulations used in various immunized rat groups according to one embodiment of the present invention.

FIG. 7B shows immunization scheme using the disclosed proteins combinations for each group for rat studies according to one embodiment of the present invention.

FIG. 7C is a graph showing F1V-specific antibody (total IgG) titers according to one embodiment of the present invention.

FIG. 7D is a graph showing PA-specific antibody (total IgG) titers according to one embodiment of the present invention.

FIG. 7E is a graph showing LeTx neutralizing antibody titers according to one embodiment of the present invention.

FIG. 8A is a graph showing survival of the rats against anthrax toxin and plague sequential challenge according to one embodiment of the present invention.

FIG. 8B is a set of in vivo imaging of infection according to one embodiment of the present invention.

FIG. 8C is a graph showing survival of the rats against anthrax LeTx and plague simultaneous challenge according to one embodiment of the present invention.

FIG. 9A is a table showing vaccine formulations used in various groups according to one embodiment of the present invention.

FIG. 9B is an immunization scheme for rabbit study according to one embodiment of the present invention.

FIG. 9C is a graph showing F1V-specific antibody (total IgG) titers on day 20 according to one embodiment of the present invention.

FIG. 9D is a graph showing F1V-specific antibody (total IgG) titers on day 42 according to one embodiment of the present invention.

FIG. 9E is a graph showing protective antigen (PA)-specific antibody (total IgG) titers according to one embodiment of the present invention.

FIG. 9F is a graph showing LeTx neutralizing antibody titer.

FIG. 9G is a graph showing survival of the rabbits challenged with 200 LD50 of aerosolized B. anthracis Ames spores according to one embodiment of the present invention.

FIG. 10A is a structural model of a bacteriophage T4.

FIG. 10B shows display of a fusion protein on a Hoc-Soc-T4 bacteriophage particle via Soc from a T4 phage or a T4-related bacteriophage according to one embodiment of the present invention.

FIG. 11 is a graph showing purification of Fimuti-PA according to one embodiment of the present invention.

FIG. 12 is a graph showing purification of Soc-PA according to one embodiment of the present invention.

FIG. 13A is a graph showing F1V-specific IgG1 antibody titers in rats according to one embodiment of the present invention.

FIG. 13B is a graph showing F1V-specific IgG2a antibody titers in rats according to one embodiment of the present invention.

FIG. 13C is a graph showing PA-specific IgG1 antibody titers in rats according to one embodiment of the present invention.

FIG. 13D is a graph showing PA-specific IgG2a antibody titers in rats according to one embodiment of the present invention.

FIG. 14A is a graph showing body weight changes in male after B. anthracis challenge (200 LD50, aerosol) according to one embodiment of the present invention.

FIG. 14B is a graph showing body weight changes in female rabbits after B. anthracis challenge (200 LD50, aerosol) according to one embodiment of the present invention.

FIG. 14C is a graph showing body temperature changes in male rabbits after B. anthracis challenge (200 LD50, aerosol) according to one embodiment of the present invention.

FIG. 14D is a graph showing body temperature changes in female rabbits after B. anthracis challenge (200 LD50, aerosol) according to one embodiment of the present invention.

BRIEF DESCRIPTION OF THE SEQUENCES

SEQ ID NO: 1 is an amino acid sequence corresponding to mutant F1mut according to one embodiment of the present invention.

SEQ ID NO: 2 is an amino acid sequence corresponding to V antigen from Y. pestis according to one embodiment of the present invention.

SEQ ID NO: 3 is an amino acid sequence corresponding to PA from B. anthracis according to one embodiment of the present invention.

SEQ ID NO: 4 is an amino acid sequence corresponding to F1mutV-PA triple antigen according to one embodiment of the present invention.

SEQ ID NO: 5 is a nucleic acid sequence encoding recombinant protein F1mutV according to one embodiment of the present invention.

SEQ ID NO: 6 is a nucleic acid sequence encoding PA according to one embodiment of the present invention.

SEQ ID NO: 7 is an amino acid sequence corresponding to furin cleavage site at PA.

SEQ ID NO: 8 is a nucleic acid sequence of a primer according to one embodiment of the present invention.

SEQ ID NO: 9 is a nucleic acid sequence of a primer according to one embodiment of the present invention.

SEQ ID NO: 10 is a nucleic acid sequence for a primer according to one embodiment of the present invention.

SEQ ID NO: 11 is a nucleic acid sequence of a primer according to one embodiment of the present invention.

SEQ ID NO: 12 is an amino acid sequence of a peptide linker according to one embodiment of the present invention.

SEQ ID NO: 13 is a nucleic acid sequence of a primer according to one embodiment of the present invention.

SEQ ID NO: 14 is a nucleic acid sequence of a primer according to one embodiment of the present invention.

SEQ ID NO: 15 is a nucleic acid sequence of RB69 Soc according to one embodiment of the present invention.

SEQ ID NO: 16 is an amino acid sequence of RB49 Soc according to one embodiment of the present invention.

SEQ ID NO: 17 is a nucleic acid sequence of fusion protein F1mutV-Soc-PA according to one embodiment of the present invention.

SEQ ID NO: 18 is an amino acid sequence of fusion protein F1mutV-Soc-PA according to one embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION Definitions

Where the definition of terms departs from the commonly used meaning of the term, applicant intends to utilize the definitions provided below, unless specifically indicated.

It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of any subject matter claimed. In this application, the use of the singular includes the plural unless specifically stated otherwise. It must be noted that, as used in the specification and the appended claims, the singular forms “a,” “an” and “the” include plural referents unless the context clearly dictates otherwise. For example, the term “a protein antigen” includes a plurality of protein antigens, including mixtures thereof. In this application, the use of “or” means “and/or” unless stated otherwise. Furthermore, use of the term “including” as well as other forms, such as “include”, “includes,” and “included,” is not limiting.

For purposes of the present invention, the term “comprising”, the term “having”, the term “including,” and variations of these words are intended to be open-ended and mean that that the compositions and methods include the recited elements, but do not exclude other elements.

For purposes of the present invention, directional terms such as “top,” “bottom,” “upper,” “lower,” “above,” “below,” “left,” “right,” “horizontal,” “vertical,” “up,” “down,” etc., are used merely for convenience in describing the various embodiments of the present invention. The embodiments of the present invention may be oriented in various ways. For example, the diagrams, apparatuses, etc., shown in the drawing figures may be flipped over, rotated by 90° in any direction, reversed, etc.

For purposes of the present invention, a value or property is “based” on a particular value, property, the satisfaction of a condition, or other factor, if that value is derived by performing a mathematical calculation or logical decision using that value, property or other factor.

For purposes of the present invention, it should be noted that to provide a more concise description, some of the quantitative expressions given herein are not qualified with the term “about.” It is understood that whether the term “about” is used explicitly or not, every quantity given herein is meant to refer to the actual given value, and it is also meant to refer to the approximation to such given value that would reasonably be inferred based on the ordinary skill in the art, including approximations due to the experimental and/or measurement conditions for such given value.

For purpose of the present invention, the term “adjacent” refers to “next to” or “adjoining something else.”

For purposes of the present invention, the term “adjuvant” refers to a composition comprised of one or more substances that enhances the immune response to an antigen(s). The mechanism of how an adjuvant operates is not entirely known. Some adjuvants are believed to enhance the immune response by slowly releasing the antigen, while other adjuvants are strongly immunogenic in their own right and are believed to function synergistically.

For purpose of the present invention, the phase “administration of a vaccine” refers to introduce a vaccine into a body of an animal or a human being. As is understood by an ordinary skilled person, it can be done in a variety of manners. For example, administration of a vaccine may be done intramuscularly, subcutaneously, intravenously, intranasally, intradermaly, intrabursally, in ovo, ocularly, orally, intra-tracheally or intra-bronchially, as well as combinations of such modalities. The dose of the vaccine may vary with the size of the intended vaccination subject.

For purposes of the present invention, the term “antigen” refers to a compound, composition, or immunogenic substance that can stimulate the production of antibodies or a T-cell response, or both, in an animal, including compositions that are injected or absorbed into an animal. The immune response may be generated to the whole molecule, or to a portion of the molecule (e.g., an epitope or hapten).

For purpose of the present invention, the term “array” refers to in vitro binding of a protein on a bacteria phage. For example, a Soc fusion protein, a protein fused with a small outer capsid protein Soc of a bacteriophage T4, may be arrayed by incubating Hoc-Soc-T4 phage particles with the Soc fusion protein to allow the Soc fusion protein to bind on Hoc-Soc-T4 phage particles.

For purposes of the present invention, the term “bind,” the term “binding” or the term “bound” refers to any type of chemical or physical binding, which includes but is not limited to covalent binding, hydrogen binding, electrostatic binding, biological tethers, transmembrane attachment, cell surface attachment and expression.

For purposes of the present invention, the term “biological sample” and the term “biological specimen” refers to either a part or the whole of a human, animal, microbe or plant in vitro or in vivo. The term includes but is not limited to material of human, animal, microbe or plant origin such as human, animal, microbial or plant tissue sections, cell or tissue cultures, suspension of human, animal, microbial or plant cells or isolated parts thereof, human or animal biopsies, blood samples, cell-containing fluids and secretion.

For purpose of the present invention, the term “bivalent” refers to a composition that has two combining sites, for example, a bivalent immunogen capable of binding to two molecules of antibodies.

For purposes of the present invention, the term “capsid” and the term “capsid shell” refers to a protein shell of a virus comprising several structural subunits of proteins. The capsid encloses the nucleic acids of the virus. Capsids are broadly classified according to their structures. The majority of viruses have capsids with either helical or icosahedral structures

For purpose of the present invention, the term “capsomere” refers to a basic substructure of a capsid, an outer covering of proteins that protects the genetic materials of a virus. Capsomeres self-assemble to form the capsid.

For purpose of the present invention, the term “cleft” refers to a groove or a V-shaped indentation that runs across two protein domains.

For purpose of the present invention, the term “correspond” and the term “corresponding” refer to that a protein sequence refer interchangeably to an amino acid position(s) of a protein. An amino acid at a position of a protein may be found to be equivalent or corresponding to an amino acid at a position of one or more other protein(s) based on any relevant evidence, such as the primary sequence context of the each amino acid, its position in relation to the N-terminal and C-terminal ends of its respective protein, the structural and functional roles of each amino acid in its respective protein, etc.

For purposes of the present invention, the term “domain” and the term “protein domain” refer to a distinct functional or structural unit in a protein. Usually, a protein domain is responsible for a particular function or interaction, contributing to the overall role of a protein. Domains may exist in a variety of biological contexts, where similar domains can be found in proteins with different functions.

For purposes of the present invention, the term “dosage” refers to the administering of a specific amount, number, and frequency of doses over a specified period of time. Dosage implies duration. A “dosage regimen” is a treatment plan for administering a drug over a period of time.

For purposes of the present invention, the term “dosage form,” the term “form,” or the term “unit dose” refers to a method of preparing pharmaceutical products in which individual doses of medications are prepared and delivered. Dosage forms typically involve a mixture of active drug components and nondrug components (excipients), along with other non-reusable material that may not be considered either ingredient or packaging.

For purposes of the present invention, the term “dose” refers to a specified amount of medication taken at one time.

For purpose of the present invention, the term “duplicate” refers to repeat or generate another identical copy of a polynucleotide sequence or an amino acid sequence.

For purpose of the present invention, the term “epitope” refers to a molecular region on the surface of an antigen capable of eliciting an immune response and combining with the specific antibody produced by such a response. It is also called “antigenic determinant.” T cell epitopes are presented on the surface of an antigen-presenting cell, where they are bound to MHC molecules.

For purposes of the present invention, the term “effective amount” or “effective dose” or grammatical variations thereof refers to an amount of an agent sufficient to produce one or more desired effects. The effective amount may be determined by a person skilled in the art using the guidance provided herein.

For purposes of the present invention, the term “engineered” refers to being made by biological engineering.

For purposes of the present invention, the term “excipient” refers to a natural or synthetic substance formulated alongside the active ingredient of a medication, included for the purpose of bulking-up formulations that contain potent active ingredients (thus often referred to as “bulking agents,” “fillers,” or “diluents”), or to confer a therapeutic enhancement on the active ingredient in the final dosage form, such as facilitating drug absorption or solubility. Excipients can also be useful in the manufacturing process, to aid in the handling of the active substance concerned such as by facilitating powder flowability or non-stick properties, in addition to aiding in vitro stability such as prevention of denaturation over the expected shelf life. The selection of appropriate excipients also depends upon the route of administration and the dosage form, as well as the active ingredient and other factors. Though excipients were at one time considered to be “inactive” ingredients, they are now understood to be “a key determinant of dosage form performance.”

For purposes of the present invention, the term “expression” and the term “gene expression” refer to a process by which information from a gene or a fragment of DNA is used in the synthesis of a functional gene product. A gene which encodes a protein will, when expressed, be transcribed and translated to produce that protein.

For purposes of the present invention, the term “expression vector,” otherwise known as an expression construct, refers to a plasmid or virus designed for protein expression in cells. The vector is used to introduce a specific gene into a target cell, and can commandeer the cell's mechanism for protein synthesis to produce the protein encoded by the gene. The plasmid is engineered to contain regulatory sequences that act as enhancer and promoter regions and lead to efficient transcription of the gene carried on the expression vector. The goal of a well-designed expression vector is the production of significant amount of stable messenger RNA, and therefore proteins.

For purpose of the present invention, the term “fragment” of a molecule such as a protein or nucleic acid refers to a portion of the amino acid or nucleotide sequence.

For purposes of the present invention, the term “furin” refers to a protein encoded by the FURIN gene. Some proteins are inactive when they are first synthesized, and must have sections deleted in order to become active. Furin deletes these sections and activates the proteins.

For purpose of the present invention, the term “fuse” refers to join together physically, or to make things join together and become a single thing.

For purpose of the present invention, the term “fusion polypeptide” or the term “fusion protein” refers to a polypeptide or a protein created through the joining of two or more genes that originally coded for separate proteins. Translation of this fusion gene results in a single or multiple polypeptides with functional properties derived from each of the original proteins. Usually, a fusion protein has at least two heterologous polypeptides covalently linked, either directly or via an amino acid linker. The heterologous polypeptides forming a fusion protein are typically linked C-terminus to N-terminus, although they can also be linked C-terminus to C-terminus, N-terminus to N-terminus, or N-terminus to C-terminus. The polypeptides of the fusion protein can be in any order and may include more than one of either or both of the constituent polypeptides. These terms encompass conservatively modified variants, polymorphic variants, alleles, mutants, subsequences, interspecies homologs, and immunogenic fragments of the antigens that make up the fusion protein. In present invention, “fusion protein” and “recombinant protein” are interchangeable. Fusion proteins of the disclosure may also comprise additional copies of a component antigen or immunogenic fragment thereof. Recombinant fusion proteins are created artificially by recombinant DNA technology for use in biological research or therapeutics.

For purposes of the present invention, the term “gel electrophoresis” refers to a method for separation and analysis of macromolecules (DNA, RNA and proteins) and their fragments, based on their size and charge. Gel electrophoresis conditions include denaturing condition and native condition (non-denaturing condition). Under denaturing condition, molecules such as proteins are denatured in a solution containing a detergent (SDS). In these conditions, for example, proteins are unfolded and coated with negatively charged detergent molecules. Proteins in SDS-PAGE are then separated on the sole basis of their size. The protein migrates as bands based on size. Each band can be detected using stains such as Coomassie blue dye or silver stain. Unlike denaturing methods, native gel electrophoresis does not use a charged denaturing agent. Under native condition, molecules such as proteins maintain their natural structures. The molecules being separated therefore differ not only in molecular mass and intrinsic charge, but also the cross-sectional area, and thus experience different electrophoretic forces dependent on the shape of the overall structure. For proteins, since they remain in the native state they may be visualized not only by general protein staining reagents but also by specific enzyme-linked staining.

For purposes of the present invention, the term “gene” refers to a nucleic acid (e.g., DNA or RNA) sequence that comprises coding sequences necessary for the production of an RNA or a polypeptide or its precursor. The term “portion,” when used in reference to a gene, refers to fragments of that gene. The fragments may range in size from a few nucleotides to the entire gene sequence minus one nucleotide.

For purpose of the present invention, the term “identical” or the term “identity” refers to the percentage of amino acid residues of two or more polypeptide sequences having the same amino acid at corresponding positions.

For purposes of the present invention, the term “immune response” refers to a specific response elicited in an animal. An immune response may refer to cellular immunity (CMI); humoral immunity or may involve both. The present invention also contemplates a response limited to a part of the immune system. Usually, an “immunological response” includes, but is not limited to, one or more of the following effects: the production or activation of antibodies, B cells, helper T cells, suppressor T cells, and/or cytotoxic T cells, directed specifically to an antigen or antigens included in the composition or vaccine of interest. Preferably, the host will display either a therapeutic or protective immunological response such that resistance to new infection will be enhanced and/or the clinical severity of the disease reduced. Such protection will be demonstrated by either a reduction or lack of symptoms normally displayed by an infected host, a quicker recovery time and/or a lowered viral titer in the infected host.

For purposes of the present invention, the term “immunity” refers to a state of resistance of a subject animal including a human to an infecting organism or substance. It will be understood that an infecting organism or substance is defined broadly and includes parasites, toxic substances, cancer cells and other cells as well as bacteria and viruses.

For purposes of the present invention, the term “immunization conditions” refers to factors that affect an immune response including the amount and kind of immunogen or adjuvant delivered to a subject animal including a human, method of delivery, number of inoculations, interval of inoculations, the type of subject animal and its condition. “Vaccine” refers to pharmaceutical formulations able to induce immunity.

For purposes of the present invention, the term “immunization dose” refers to the amount of antigen or immunogen needed to precipitate an immune response. This amount will vary with the presence and effectiveness of various adjuvants. This amount will vary with the animal and the antigen, immunogen and/or adjuvant. The immunization dose is easily determined by methods well known to those skilled in the art, such as by conducting statistically valid host animal immunization and challenge studies.

For purposes of the present invention, the term “immunogen,” the term “immunogenic composition,” or the term “immunological composition” refers to a substance or material (including antigens) that is able to induce an immune response alone or in conjunction with an adjuvant. Both natural and synthetic substances may be immunogens.

For purposes of the present invention, the term “immunogenicity” refers to the ability to of a particular substance, such as an antigen or epitope, to provoke an immune response in the body of a human or animal. In other words, immunogenicity is the ability to induce a humoral and/or cell-mediated immune responses.

For purposes of the present invention, the term “individual” refers to a mammal. For example, the term “individual” may refer to a human individual.

For purposes of the present invention, the term “immunogenic amount” is an amount of an antigen preparation of interest or amount of a biological toxin that elicits a clinically detectable protective response in an animal.

For purposes of the present invention, the term “junction,” the term “junction fragment,” the term “junction sequence,” and the term “junction peptide” are interchangeable and refer to a region or a fragment or a portion of peptide between two subunits or sections within a polypeptide. The two subunits or sections meet or join via the junction fragment.

For purpose of the present invention, the term “linked” refers to a covalent linkage between two polypeptides in a fusion protein. The polypeptides are typically joined via a peptide bond, either directly to each other or via one or more additional amino acids.

For purpose of the present invention, the term “linker” refers to short peptide sequences that occur between functional protein domains and link the functional domains together. Linkers designed by researchers are generally classified into three categories according to their structures: flexible linkers, rigid linkers, and in vivo cleavable linkers. A flexible linker is often composed of flexible residues like glycine and serine so that the adjacent protein domains are free to move relative to one another. A linker also may play a role in releasing the free functional domain in vivo (as in in vivo cleavable linkers). Linkers may offer many other advantages for the production of fusion proteins, such as improving biological activity, increasing expression yield, and achieving desirable pharmacokinetic profiles. The composition and length of a linker may be determined in accordance with methods well known in the art and may be tested for efficacy.

For purposes of the present invention, the term “modified” and the term “mutant” when made in reference to a gene or to a gene product refer, respectively, to a gene or to a gene product which displays modifications in sequence and/or functional properties (i.e., altered characteristics) when compared to the wild-type gene or gene product.

For purpose of the present invention, the term “monomer” refers to a molecule that may bind chemically to other molecules to form a polymer. The term “monomeric protein” may also be used to describe one of the proteins making up a multiprotein complex

For purposes of the present invention, the term “multivalent” refers to a vaccine containing more than one antigen whether from the same species (i.e., different isolates of Mycoplasma hyopneumoniae), from a different species (i.e., isolates from both Pasteurella hemolytica and Pasteurella multocida), or a vaccine containing a combination of antigens from different genera (for example, a vaccine comprising antigens from Pasteurella multocida, Salmonella, Escherichia coli, Haemophilus somnus and Clostridium).

For purposes of the present invention, the term “mutation” refers to a change in the polypeptide sequence of a protein or in the nucleic acid sequence.

For purpose of the present invention, the term “oligomer” refers to a molecular complex that consists of a few monomer units. Dimers, trimers, and tetramers are, for instance, oligomers respectively composed of two, three and four monomers. An oligomer can be a macromolecular complex formed by non-covalent bonding of few macromolecules like proteins or nucleic acids. In this sense, a homo-oligomer would be formed by few identical molecules and by contrast, a hetero-oligomer would be made of three different macromolecules.

For purpose of the present invention, the term “oligomerization” refers to a chemical process that converts monomers to macromolecular complexes through a finite degree of polymerization.

For purposes of the present invention, the term “operably linked,” the term “operably associated,” and the term “functionally linked” are used interchangeably and refer to a functional relationship between two or more DNA segment. Particularly, “operably linked” may refer to place a first nucleic acid sequence in a functional relationship with the second nucleic acid sequence. For example, a promoter/enhancer sequence, including any combination of cis-acting transcriptional control elements is operably associated to a coding sequence if the promoter/enhancer sequence affects the transcription or expression of the coding sequence in an appropriate host cell or other expression system. Promoter regulatory sequences that are operably linked to the transcribed gene sequence are physically contiguous to the transcribed sequence.

For purposes of the present invention, the term “nucleic acid” and the term “polynucleotide,” as used interchangeably herein, refer to polymers of nucleotides of any length, and include DNA and RNA. The nucleic acid bases that form nucleic acid molecules can be the bases A, C, G, T and U, as well as derivatives thereof. Derivatives of these bases are well known in the art. The term should be understood to include, as equivalents, analogs of either DNA or RNA made from nucleotide analogs. The term as used herein also encompasses cDNA, that is complementary, or copy, DNA produced from an RNA template, for example by the action of reverse transcriptase. A polynucleotide may comprise modified nucleotides, such as methylated nucleotides and their analogs.

For purposes of the present invention, the term “parenteral route” refers to the administration of a composition, such as a drug in a manner other than through the digestive tract. Parenteral routes include routes such as intravenous, intra-arterial, transdermal, intranasal, sub-lingual and intraosseous, etc. For example, intravenous is also known as I.V., which is giving directly into a vein with injection. As the drug directly goes into the systemic circulation, it reaches the site of action resulting in the onset the action.

For purposes of the present invention, the term “pharmaceutically acceptable” refers to a compound or drug approved or approvable by a regulatory agency of a federal or a state government, listed or listable in the U.S. Pharmacopeia or in other generally recognized pharmacopeia for use in mammals, including humans. For example, a “pharmaceutically acceptable diluent, excipient, carrier, or adjuvant” is a diluent, excipient, carrier, or adjuvant which is physiologically acceptable to the subject while retaining the therapeutic properties of the pharmaceutical composition with which it is administered. One exemplary pharmaceutically acceptable carrier is physiological saline. Other physiologically acceptable diluents, excipients, carriers, or adjuvants and their formulations are known to one skilled in the art (see, e.g., U.S. Pub. No. 2012/0076812).

As used herein, the terms “pharmaceutically acceptable carrier” and “pharmaceutically acceptable vehicle” are interchangeable and refer to refers to any carrier that does not itself induce the production of antibodies harmful to an individual or a subject receiving a composition. Suitable pharmaceutically acceptable carriers known in the art include, but are not limited to, sterile water, saline, glucose, dextrose, or buffered solutions. Carriers may include auxiliary agents including, but not limited to, diluents, stabilizers (i.e., sugars and amino acids), preservatives, wetting agents, emulsifying agents, pH buffering agents, viscosity enhancing additives, colors and the like.

For purpose of the present invention, the term “polymer” refers to a compound or a mixture of compounds comprising many repeating subunits, known as monomers.

For purpose of the present invention, the terms “polypeptide” and “protein” are used interchangeably herein to refer to a polymer of amino acid residues. The terms encompass amino acid polymers in which one or more amino acid residues are artificial chemical mimetic of a corresponding naturally occurring amino acids, as well as to naturally occurring amino acid polymers and non-naturally occurring amino acid polymer.

For purpose of the present invention, the term “protein domain” refers to a distinct functional or structural unit in a protein. Usually, a protein domain is responsible for a particular function or interaction, contributing to the overall role of a protein. Domains may exist in a variety of biological contexts, where similar domains can be found in proteins with different functions.

For purposes of the present invention, the term “protein purification” refers to a series of processes intended to isolate one or a few proteins from a complex mixture, such as cell culture media, cells, tissues or whole organisms, etc. Usually a protein purification protocol contains one or more chromatographic steps. The basic procedure in chromatography is to flow the solution containing the protein through a column packed with various materials. Different proteins interact differently with the column material, and can thus be separated by the time required to pass the column, or the conditions required to elute the protein from the column. Many purification strategies exist. For example, a protein can be attached with an antigen peptide tag by engineering and be purified using an antibody against the antigen peptide tag. Usually, during purification, the protein with an antigen peptide tag can be added on a column loaded with resin that is coated with an antibody or by incubating with a loose resin that is coated with an immobilizing antibody. This particular procedure is known as immunoprecipitation. Immunoprecipitation is quite capable of generating an extremely specific interaction which usually results in binding only the desired protein. The purified tagged proteins can then easily be separated from the other proteins in solution and later eluted back into clean solution.

For purposes of the present invention, the term “purified” refers to the component in a relatively pure state, e.g. at least about 90% pure, or at least about 95% pure, or at least about 98% pure.

For purpose of the present invention, the term “recombinant protein” refers to a protein derived from a recombinant DNA, that is, it's code is carried by a “recombinant DNA” molecule. Recombinant DNA molecules are DNA molecules formed by laboratory methods of genetic recombination (such as molecular cloning) to bring together genetic material from multiple sources, creating sequences that would not otherwise be found in biological organisms.

For purpose of the present invention, the term “recombinant vaccine” refers to a vaccine made by genetic engineering, the process and method of manipulating the genetic material of an organism. Usually, a recombinant vaccine encompasses one or more protein antigens that have either been produced and purified in a heterologous expression system (e.g., bacteria or yeast) or purified from large amounts of the pathogenic organism. The vaccinated person produces antibodies to the one or more protein antigens, thus protecting him/her from disease.

For purposes of the present invention, the term “stimulate,” the term “immuno-stimulate” refers to induce the activation or increase the activity of any components in an immune system. For example, T cell activation requires at least two signals to become fully activated. The first occurs after engagement of the T cell antigen-specific receptor (TCR) by the antigen-major histocompatibility complex (MHC), and the second by subsequent engagement of co-stimulatory molecules. Once stimulated, the T cells will recognize the antigen or vaccine used during stimulation or activation of the T cells.

For purpose of the present invention, the term “subunit” refers to a separate polypeptide chain that makes a certain protein which is made up of two or more polypeptide chains joined together. In a protein molecule composed of more than one subunit, each subunit can form a stable folded structure by itself. The amino acid sequences of subunits of a protein can be identical, similar, or completely different.

For purpose of the present invention, the term “subject” or the term “individual” refers interchangeably to a mammalian organism, such as a human, mouse, etc., that is administered a mutant protein of the present invention for a therapeutic or experimental purpose.

For purpose of the present invention, the term “suitable vector” refers to any vector (for example, a plasmid or virus) which may incorporate a nucleic acid sequence encoding an antigenic polypeptide and any desired control sequences. It may bring about the expression of the nucleic acid sequence. The choice of the vector will typically depend on the compatibility of the vector with a host cell into which the vector is to be introduced.

For purpose of the present invention, the term “type three secretion system (T3SS)” refers to a protein appendage found in Yersinia, a genus of Gram-negative rod shaped bacteria that cause the plague. T3SS is also called “injectisome” or “injectosome,” with a needle-like structure used as a sensory probe to detect the presence of eukaryotic organisms and secrete proteins that help the bacteria infect them. T3SS are essential for the pathogenicity of many pathogenic bacteria.

For purpose of the present invention, the term “transplant” refers to move or transfer a fragment of a DNA or a protein to another place or situation. For example, the NH2-terminal amino acid residues of a protein may be “transplanted” to the COOH-terminus of the protein by deleting the NH2-terminal amino acid residues and fusing them to the COOH-terminus of the protein via a short linker wherein the short linker joins the deleted NH2-terminal amino acid residues to the COOH-terminus of the protein.

For purposes of the present invention, the term “targeting ligand” refers to proteins or receptors displayed on the surface of cells like dendritic cells and antigen-presenting cells. The binding of a targeting ligand to an antigen-presenting or dendritic cell is required for cellular activation and induction of a variety of downstream effects.

For purposes of the present invention, the term “targeting molecule” refers to a naturally existing cellular or molecular structure involved in the pathology of interest that the drug-in-development is meant to act on.

For purpose of the present invention, the term “vaccine” refers to a biological compound that improves immunity to a particular disease. A vaccine typically contains an agent that resembles a disease-causing microorganism (microbe), such as virus, bacteria, fungus, etc. Traditionally, it is often made from weakened or killed forms of the microbe, its toxins, or one of its surface proteins. The agent injected into a human or animal body stimulates the body's immune system to recognize the agent as foreign, destroy it, and keep a record of it, so that the immune system can more easily recognize and destroy any of these microorganisms that it later encounters.

As used herein, the term “vaccine composition” includes at least one antigen or immunogen in a pharmaceutically acceptable vehicle useful for inducing an immune response in a host. Vaccine compositions can be administered in dosages and by techniques well known to those skilled in the medical or veterinary arts, taking into consideration such factors as the age, sex, weight, species and condition of the recipient animal, and the route of administration. The route of administration can be percutaneous, via mucosal administration (e.g., oral, nasal, anal, vaginal) or via a parenteral route (intradermal, transdermal, intramuscular, subcutaneous, intravenous, or intraperitoneal). Vaccine compositions can be administered alone, or can be co-administered or sequentially administered with other treatments or therapies. Forms of administration may include suspensions, syrups or elixirs, and preparations for parenteral, subcutaneous, intradermal, intramuscular or intravenous administration (e.g., injectable administration) such as sterile suspensions or emulsions. Vaccine compositions may be administered as a spray or mixed in food and/or water or delivered in admixture with a suitable carrier, diluent, or excipient such as sterile water, physiological saline, glucose, or the like. The compositions can contain auxiliary substances such as wetting or emulsifying agents, pH buffering agents, adjuvants, gelling or viscosity enhancing additives, preservatives, flavoring agents, colors, and the like, depending upon the route of administration and the preparation desired. Standard pharmaceutical texts, such as “Remington's Pharmaceutical Sciences,” 1990 may be consulted to prepare suitable preparations, without undue experimentation.

For purposes of the present invention, the term “variant” refers to a polypeptide or a nucleic acid sequence encoding a polypeptide that has one or more conservative amino acid variations or other minor modifications such that the corresponding polypeptide has substantially equivalent function when compared to the wild-type polypeptide. For purposes of the present invention, the term “conservative variation” denotes the replacement of an amino acid residue by another biologically similar residue, or the replacement of a nucleotide in a nucleic acid sequence such that the encoded amino acid residue does not change or is another biologically similar residue. Examples of conservative variations include the substitution of one hydrophobic residue, such as isoleucine, valine, leucine or methionine for another hydrophobic residue, or the substitution of one polar residue, such as the substitution of arginine for lysine, glutamic acid for aspartic acid, or glutamine for asparagine, and the like. The term “conservative variation” also includes the use of a substituted amino acid in place of an unsubstituted parent amino acid provided that antibodies raised to the substituted polypeptide also immunoreact with the unsubstituted polypeptide.

For purposes of the present invention, the term “virus” refers to an infectious agent that is unable to grow or reproduce outside a host cell and that infects mammals (e.g., humans) or birds.

For purposes of the present invention, the term “virus particle” refers to viruses and virus-like organisms.

DESCRIPTION

While the invention is susceptible to various modifications and alternative forms, specific embodiment thereof has been shown by way of example in the drawings and will be described in detail below. It should be understood, however that it is not intended to limit the invention to the particular forms disclosed, but on the contrary, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and the scope of the invention.

Bacillus anthracis and Yersinia pestis are two Tier-1 biothreat agents that pose a great risk to United States' national security and public health due to their exceptionally high virulence.¹⁻⁴ Bacillus anthracis and Yersinia pestis are two of the deadliest bioterror agents. B. anthracis, a Gram-positive bacterium, is the causative agent of anthrax, and Y. pestis, a Gram-negative bacterium, is the etiological agent of plague. Both are deadly diseases and cause rapid death, in 3-6 days, of 85-100% of exposed individuals, unless antibiotics are administered within 20-24 hours after the onset of symptoms.¹⁻⁵ Intentional release of these organisms as a bioweapon could lead to massive deaths, public panic, and social chaos.¹⁻⁴ The best way to offset such an attack is to vaccinate people prior to the attack. Vaccination is also essential after the attack to minimize further casualties and to mitigate additional attacks.⁶ Consequently, since the anthrax attacks of September 2001, stockpiling of vaccines against anthrax and plague has been a national priority but none have yet been licensed.¹⁻⁴

There are currently no Food and Drug Administration (FDA) approved anthrax or plague vaccines for mass vaccination in humans. The BioThrax vaccine approved for anthrax in 1970s, AVA (anthrax vaccine alum-adsorbed), has been used for high risk individuals such as the military.⁷ This vaccine consists of a filtered crude culture supernatant of B. anthracis strain V770-NP1-R, but it exhibits significant reactinogenicity in vaccinated individuals.⁷⁻⁹ A re-formulated version of BioThrax vaccine (Emergent BioSolutions, Gaithersburg, Md.) was recently approved for humans (18-65 years of age) to prevent disease following suspected or confirmed exposure to B. anthracis in conjunction with recommended antibiotic treatment(s).¹⁰ The use of this reformulated vaccine is also currently limited to military and high-risk healthcare workers.¹⁰ Unfortunately, these vaccines require multiple initial doses and subsequent boosters to maintain protective immunity.⁷

Similarly, a killed whole cell (KWC) plague vaccine was in use in the past, also for military and laboratory personnel in the United States, but was discontinued due to high reactinogenicity, and because its protective effect against bubonic plague did not extend to the deadlier pneumonic form of the disease.¹¹ A live-attenuated plague vaccine, EV76, which is protective against both bubonic and pneumonic plague is used in some parts of the world where plague is endemic, but it is also associated with severe side effects.¹²

In recent years, the focus has been shifted to subunit vaccines containing pure recombinant proteins. FIG. 1A and FIG. 1B are schematic illustrations of anthrax toxin pathway and Yersinia pestis surface components targeted for vaccine design. FIG. 1A is a schematic illustration of anthrax toxin pathway. The protective antigen (PA), a key component of the lethal toxin (LeTx) of Bacillus anthracis, has been the principal target for anthrax vaccines.^(8,9) As shown in FIG. 1A, PA is the host receptor-binding component of the tripartite anthrax toxin that consists, in addition, of lethal factor (LF) and edema factor (EF)¹³ (FIG. 1A). Once bound to the host receptors CMG2 and TEM8, PA is cleaved by furin to generate PA20 (20 kDa) and PA63 (63 kDa). PA63 then oligomerizes to produce a heptamer or octamer that then interacts with lethal factor (LF) and edema factor (EF) to form the LeTx or edema toxin (EdTx), respectively. Translocation of LF and EF through the PA heptamer/octamer channel into the host cell cytosol results in toxic effects. Numerous studies have documented that antibodies against PA alone are sufficient to completely protect animals against lethal, aerosolized B. anthracis Ames spore challenge.^(6,14) However, the instability of recombinant PA (rPA) when adsorbed on aluminum hydroxide gel and the variable immune responses in humans remained as a barrier for licensing a rPA anthrax vaccine.^(15,16)

FIG. 1B is a schematic illustration of Y. pestis surface components targeted for vaccine design. As shown in FIG. 1B, F1 is the structural unit of the capsular layer. V forms a pore at the tip of the injectisome needle and facilitates translocation of Yersinia outer proteins (Yops) into the host cell. F1 and V are two principal targets for the plague subunit vaccines. Recombinant plague vaccines typically combine two surface-exposed antigens of Y. pestis, the capsular protein Caf1 (or F1; 15.6 kDa) and the low calcium response V antigen, LcrV (or V; 37.2 kDa).^(11,17) F1 assembles into fibers to form an outer capsular layer, allowing the bacterium to adhere to the host cell and escape phagocytosis.¹⁸ The V antigen forms an oligomeric “pore” at the tip of the “injectisome” needle of the Y. pestis type 3 secretion system (T3SS) through which the effector proteins (Yersinia outer proteins or Yops) are delivered into the host cell cytosol.¹⁹ Antibodies against F1 and V provide protection against Y. pestis infection, although, based on literature, cellular immunity also seems to play a role in providing protective immunity.^(11,17) Two types of recombinant F1/V vaccines have been formulated; a mixture of F1 and V proteins, or a single protein containing both F1 and V, the F1-V fusion protein.²⁰⁻²² A major concern for licensing these vaccines is that the fibrous F1 protein forms heterogeneous aggregates that might compromise the quality of the vaccines and lead to variable and insufficient immune responses.^(21,23,24)

Previously, researchers tried to use a mixture of F1, V, and PA antigens. However, the same immunized animals have not been tested for protection against both anthrax and plague pathogens. Another major problem in developing these biodefense vaccines is the need for two separate vaccines requiring two completely different manufacturing processes. For national preparedness against potential bioterror threats, it would be highly beneficial to design a multivalent vaccine that can provide protection against both of pathogens, B. anthracis and Y. pestis. Such a vaccine would require a single manufacturing process, fewer immunizations, and would be cost-effective. It would also greatly reduce time and effort in expensive human clinical trials and the downstream licensing and other regulatory processes. Furthermore, and perhaps most significant, it would streamline the systems for stockpiling, field delivery, and mass vaccination of humans.

Recently, the present inventors reported two new approaches to overcome some of the problems associated with the recombinant anthrax and plague vaccines.^(23,25) Using structure-based immunogen design, a mutant (mut) F1 which folds into a soluble monomer rather than a fiber, without diminishing its immunogenicity, is engineered.^(23,25) The monomeric F1 in combination with V (F1mutV fusion protein; 56 kDa) provided complete protection against highly lethal Y. pestis CO92 challenge in mice and Brown Norway rat models of pneumonic plague.²³ In parallel, a novel nanoparticle antigen display and delivery system using bacteriophage T4 is developed.^(23,25-27) The 120×86 nm size T4 head (capsid) is decorated with 870 molecules of the nonessential small outer capsid protein or Soc (9 kDa).²⁸ Soc assembles as a trimer and clamps adjacent capsomers (a molecular clamp), reinforcing and further stabilizing an already stable T4 head.²⁹ PA (or F1mutV) fused to the N- or C-termini of Soc can be displayed on Soc-T4 head with high affinity and exquisite specificity.^(23,25,27,30) Such nanoparticles arrayed with the antigen molecules using our defined in vitro assembly system are highly immunogenic.^(23,31) These particles elicited a robust immune response in the absence of an adjuvant^(23,31,32) and provided complete protection against lethal inhalational anthrax or pneumonic plague challenges in multiple animal models.^(23,32)

Embodiments disclosed herein provide two approaches to design a single biodefense vaccine against inhalation anthrax and pneumonic plague. Generally, the first approach involves engineering a bivalent immunogenic composition comprising a fusion protein. The fusion protein is a triple antigen containing all three antigens, i.e., F1 and V from Y. pestis and PA from B. anthracis that is able to fold into a soluble protein and retain full functionality. For example, this fusion protein may be constructed by recombinantly fusing all three genes for mutated F1,²⁶ V,²¹ and PA²⁸. The fusion protein requires a single process for vaccine manufacture. The second approach involves preparation of bacteriophage nanoparticles arrayed with all three antigens, i.e., F1 and V from Y. pestis and PA from B. anthracis that is able to fold into a soluble protein and retain full functionality. For example, a single vaccine may comprise T4 bacteriophage (or T4 phage) nanoparticles that display these three immunogens on the virus surface of the T4 phage nanoparticles. The bacteriophage nanoparticles arrayed with all three antigens may be used as a vaccine without adjuvant.

Both the vaccines disclosed herein have been demonstrated to provide protection against sequential or simultaneous challenge with both anthrax and plague pathogens. For example, both the soluble triple fusion and T4 nanoparticle vaccines generate robust antigen-specific immune responses and provided near complete protection against anthrax and plague in three different animal models. Furthermore, the T4 nanoparticles generate balanced T_(H)1- and T_(H)2-based antibody responses, a highly desirable trait for any vaccine, but particularly important for protection against plague.¹¹ By using a dual challenge model in which the animals are simultaneously administered with lethal doses of both anthrax lethal toxin (LeTx) and Y. pestis CO92, the disclosed vaccines provide complete protection against anthrax and plague. For example, in some embodiment, two doses of these disclosed vaccines elicit robust immune responses in mice, rats, and rabbits, and confer complete protection in animal models of inhalational anthrax and pneumonic plague.

The present disclosure provides the first proof-of-concept data that a dual anthrax-plague vaccine can potentially protect vaccinees in the event of a bioterror attack with weaponized B. anthracis and/or Y. pestis. These dual vaccines (bivalent vaccine), therefore, are strong candidates for stockpiling as part of national preparedness against bioterrorism threats.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

Bivalent Immunogenic Composition Comprising a Triple Fusion Protein

FIG. 2A is a schematic illustrating protective antigen (PA) and F1mutV-PA recombinant constructs according to one embodiment of the present invention. As shown in FIG. 2A, PA (83 kDA) 210 comprises multiple domains including PA20 domain 220, PA63 domain 230, and PA domain IV 240. Furin cleavage site shown as an arrow locates between the PA20 domain 220 and the PA63 domain 230. The Furin cleavage site

Generally, the first approach involves engineering a bivalent (or dual) immunogenic composition comprising a triple fusion protein These three antigens are able to fold into a soluble protein and retain full functionality.

In one embodiment, a triple fusion protein containing all three antigens, i.e., F1 and V from Y. pestis and PA from B. anthracis, is constructed by recombinantly fusing all three genes for mutated F1,²⁶ V,²¹ and PA²⁸ in-frame. The goal is to retain the structural and functional integrity of all three antigens so that each antigen's immunogenicity and protective efficacy is not compromised. As a result, each antigen comprised in the triple fusion protein keeps its immunogenicity and protective efficacy. This triple fusion protein may be used as an immunogenic component to create a dual anthrax-plague vaccine, or bivalent anthrax-plague vaccine.

F1mutV-PA shown in FIG. 2A is an exemplary triple fusion protein comprising a mutated F1 and a V antigen from Yersinia pestis and a protective antigen (PA) from B. anthracis fused in-frame. The mutated F1 is fused in-frame to the N-terminus of the V antigen via a first linker, and the V antigen is fused in-frame to the N-terminus of PA via a second linker. The triple fusion protein has immunogenicity of the mutated F1, immunogenicity of the V antigen, and immunogenicity of the PA. Fusion protein F1mutV-PA is able to be cleaved by furin, resulting in cleavage products, of which one is F1mutV-PA20 280 and another one is PA63 domain 230 with PA domain IV 240. The furin cleavage site at PA residues comprises RKKR (SEQ ID NO: 7).

In one embodiment, in the above described triple fusion protein, the C-terminus of a previously constructed F1mutV (56 kDa) antigen 270^(23,25) is fused to the N-terminus of PA (83 kDa) with a flexible linker in the middle. In one embodiment, the flexible linker comprises Glu-Ala-Ser-Ala (SEQ ID NO: 12). In one embodiment, the F1mut shown in FIG. 2A is previously designed by deleting the N-terminal β-strand residues 1-14 of native F1 antigen and fusing them to the C-terminus of native F1 antigen with a linker, such as a Ser-Ala linker, in between. Consequently, the β-strand is reoriented such that it fits into its own β-sheet cleft (intramolecular complementation) rather than that of the adjacent F1 subunit. In addition, residues 15-21 of native F1 are duplicated at the C-terminal end to restore any potential T-cell epitope that might have been compromised during the β-strand switch. As a result, F1mut folds into a monomer instead of polymerizing as a linear fiber and retains full immunogenicity.^(26, 29)

In one embodiment, the F1mut has a polypeptide sequence set forth in SEQ ID NO: 1. The V antigen and PA sequences of the triple antigen correspond to native full-length sequences.^(21, 28) The V antigen has a polypeptide sequence set forth in SEQ ID NO: 2 and PA has a polypeptide sequence set forth in SEQ ID NO: 3. In one embodiment, the triple fusion protein F1mutV-PA comprises a sequence set forth in SEQ ID NO: 4.

FIG. 2B is a structural model of F1mutV-PA triple antigen according to one embodiment of the present invention. The model is manually generated using Chimera with structures of V antigen (PDB ID: 1Z9S), V antigen (PDB ID: 4JBU), and PA (PDB ID: 1ACC). Based on structural and bioinformatics analyses, this orientation is predicted to be optimal because the C-terminal PA domain IV, which recognizes the host receptors CMG2 (capillary morphogenesis gene-2) and TEM8 (tumor endothelial marker-8), will encounter minimal, if any, steric hindrance.^(30,31)

Recognition of these receptors is the first step in the anthrax toxin intoxication pathway within the host cell and essential for furin cleavage of the N-terminal domain of PA to generate PA20 (20 kDa) and PA63 (63 kDa) (FIG. 1A and FIG. 1B).³⁵ PA63 oligomerizes to produce heptamers and octamers that then interacts with lethal factor (LF) and edema factor (EF) (FIG. 1A).¹³ Although in the construct the F1mutV protein is attached to the N-terminus of PA (FIG. 2A), based on the linear domain arrangement of F1 and V proteins as determined by the X-ray structures,^(55,56) the furin cleavage site at PA residues RKKR (SEQ ID NO: 7 (amino acids (aa) 164-167) should remain accessible to the protease (FIG. 2B).

Embodiments further provide various vectors for expression the triple fusion protein described above. A vector may have a regulatory region operably linked to a nucleic acid sequence encoding the triple fusion protein described above. The regulatory region regulates the expression of the triple fusion protein in a cell carrying the vector. In some embodiment, the expression of the recombinant is regulated under a regulatory region comprising an inducible promoter, and the triple fusion protein is not consistently expressed in a cell carrying the vector but can be induced as needed. In some embodiment, the expression of a recombinant protein described herein in a cell carrying the vector is controlled under a constitutively promoter.

In some embodiment, bivalent (dual) anthrax-plague vaccine may be developed from the above described triple fusion protein. An immunogenic composition may comprise the above described triple fusion protein containing all three antigens, i.e., F1 and V from Y. pestis and PA from B. anthracis, fused in frame. For example, an immunogenic composition my include F1mutV-PA (SEQ ID NO: 4) as immunogenic component. An immunogenic composition comprising a triple fusion protein such as F1mutV-PA (SEQ ID NO: 4) may further include a pharmaceutical acceptable carrier or excipient. Alternatively, an immunogenic composition comprising a triple fusion protein such as F1mutV-PA (SEQ ID NO: 4) may further include an adjuvant and be used as a vaccine to provide protection against sequential or simultaneous challenge with both anthrax and plague pathogens. In some embodiment, the tripe fusion protein F1mutV-PA can be adjuvanted with Alum or another licensed adjuvant using the already established processes in vaccine manufacturing. F1mutV-PA may be adjuvanted with liposomes or Alum-liposomes mixture.

In some embodiments, the triple fusion protein contained in the immunogenic composition is purified. One skilled in the art of preparing formulations can readily select the proper form and mode of administration depending upon the particular characteristics of the vaccine selected, the disorder or condition to be treated, the stage of the disorder or condition, and other relevant circumstances.

Bivalent Vaccine Comprising Bacteriophage Nanoparticles Arrayed with Three Antigens

FIG. 10A is a structural model of a bacteriophage T4. The enlarged capsomer 1000 shows a major capsid protein gp23* (“*” represents a cleaved form) (930 copies), Soc (870 copies), and Hoc (155 copies). The portal vertex (not visible in the picture) connects the head to the tail. The unique architecture of bacteriophage T4 capsid (T (triangulation number)=20; width, 86 nm; length, 119.5 nm) with two non-essential outer capsid proteins, Hoc (highly antigenic outer capsid protein; 39 kDa) and Soc (small outer capsid protein; 9 kDa), provides a suitable platform for multicomponent antigen display. Hoc and Soc decorate the capsid, which is composed of the major capsid protein, gp23* (“*” represents the cleaved mature capsid protein) (49 kDa, 930 copies), the vertex protein, gp24* (46 kDa, 55 copies), and the portal protein, gp20 (61 kDa, 12 copies). Hoc, a dumbbell shaped protrusion at the center of the gp23* hexon, is a monomer present at up to 155 copies per capsid, whereas Soc, a small protrusion at the interface of adjacent hexons, is a trimer present at up to 810 copies per capsid. These proteins bind to the capsid sites, which appear after maturation cleavages of the capsid proteins and capsid expansion. These proteins, especially Soc, stabilize the capsid against extremes of pH (>10.5), but are not required for phage viability or infectivity.³⁰

FIG. 10B shows display of a fusion protein on a Hoc-Soc-T4 bacteriophage particle via Soc from a T4 phage or a T4-related bacteriophage. Enlarged capsomers show models of capsomes before and after the fusion protein display. Upon binding of a fusion protein, such as a Soc fusion protein, the T4 phage particle is decorated with the fusion protein and displays the fusion protein on its capsid.

According to embodiments, an immunogenic composition may comprise one or more bacteriophage nanoparticles arrayed with one or more Soc fusion proteins on capsid surface of each bacteriophage nanoparticle. The one or more Soc fusion proteins may comprise a Soc fused to an antigen selected from the group consisting of a mutated F1 antigen from Yersinia pestis, a V antigen from Yersinia pestis, a protective antigen (PA) from B. anthracis, and combination thereof. The bacteriophage nanoparticles may be a T4 phage or a relative of T4 phage. The Soc may be from T4 bacteriophage or a relative of T4 bacteriophage such as phage RB49.

Soc fusion proteins may be constructed by fusing a small outer capsid protein of a bacteriophage T4 or a T4-related phage to an antigen via a linker. In some embodiments, the small outer capsid protein of a T4phage or a T4-related phage may be Soc from T4 phage or from T4-related bacteriophage RB69. As shown in FIGS. 10A and 10B, the small outer capsid protein of a bacteriophage T4 or a T4-related phage provides a nanoplatform for symmetrical arraying of the antigen on the surface of a bacteriophage T4 or a T4-related phage as a fusion protein.

In some embodiments, an antigen may be fused to a Soc protein from a T4 phage or a T4-related phage RB69 via a linker. In some embodiment, the linker may be a two amino acid linker Gly-Ser.

In some embodiment, the above described Soc protein may be a Soc fusion protein encompassing mutated F1 antigen from Yersinia pestis, V antigen from Yersinia pestis, and/or PA from B. anthracis. In some embodiments, a mutated antigen such as mutated F1 antigen may be fused to a Soc protein from a T4 phage or a T4-related phage RB69 via a linker. For example, a Soc protein may be a T4-related phage RB69 Soc having an amino acid sequence set forth in SEQ ID NO: 15. The Soc protein may be encoded by a nucleotide sequence of SEQ ID NO: 16. The linker used for fusing a Soc protein with an antigen such as a mutated F1 may comprise a two amino acid linker Gly-Ser.

Specifically, embodiments further provide recombinant proteins constructed by fusing mutated F1 antigen, V antigen, and PA with RB49 Soc in-frame. In one embodiment, these Soc fusion proteins include F1mutV-Soc-PA (148 kDa), F1mutV-Soc (66 kDa), Soc-PA (93 kDa), etc.

In one embodiment, the above described immunogenic composition comprises a Soc fusion protein which is a recombinant protein F1mutV-Soc-PA. The recombinant protein F1mutV-Soc-PA including a mutated F1 antigen and a V antigen from Yersinia pestis, a Soc, and a PA. The mutated F1 antigen is fused in-frame to the N-terminus of the V antigen, the V antigen is fused in-frame to N-terminus of the Soc, and the Soc is fused in-frame to the N-terminus of PA. In one embodiment, fusion protein F1mutV-Soc-PA has an amino acid sequence set forth in SEQ ID NO: 18. In one embodiment, the fusion protein F1mutV-Soc-PA is encoded by a nucleotide sequence set forth in SEQ ID NO: 17. In one embodiment, each bacteriophage nanoparticle of the one or more bacteriophage nanoparticles described above is arrayed with the recombinant protein F1mutV-Soc-PA on capsid surface.

The recombinant protein F1mutV-Soc including a mutated F1 antigen, a V antigen, and a Soc. The mutated F1 antigen is fused in-frame to the N-terminus of V antigen to thereby and the V antigen is fused in-frame to the N-terminus of the Soc. Soc fusion protein Soc-PA comprise a Soc fused in-frame to the N-terminus of PA. The Soc protein described above may be from a T4 phage or a T4-related bactgeriophage such as RB69. Various peptide linkers may be used in constructing the various Soc fusion proteins.

In some embodiments of the present invention, a native V antigen of Yersinia pestis is fused to a Soc protein from a T4 phage and/or a T4-related bactgeriophage RB69 via a linker, resulting a recombinant protein V-Soc. A two amino acid linker Gly-Ser may be used between V antigen and Soc, wherein a C-terminus of the linker is directly linked to an NH2-terminus of the Soc protein from a T4 phage and/or a T4-related bacteriophage RB69 and an NH2-terminus of the linker is directly linked to a C-terminus of the V antigen of Yersinia pestis.

In one embodiment of the present invention, the above described Soc fusion protein may be expressed in cells, including and bacteria E. Coli cells, and be purified from cell-free lysates of cell cultures. The purified Soc fusion proteins may be then arrayed on the capsid surface of a bacteriophage nanoparticle.

The above described recombinant proteins, for example, F1mutV-Soc-PA, F1mutV-Soc, and Soc-PA, may be assembled on one or more T4 nanoparticles through three different ways: i) display of F1mutV-Soc-PA on the capsid surface of a T4 nanoparticle, ii) display of F1mutVSoc and Soc-PA on the same capsid surface of a T4 nanoparticle, and iii) a 1:1 mixture of T4 phage particles separately displayed with F1mutV-Soc or Soc-PA.

Accordingly, in one embodiment, the Soc fusion proteins, i.e., F1mutV-Soc and the Soc-PA are arrayed on the same capsid of bacteriophage nanoparticle. In one embodiment, the above described Soc fusion proteins F1mutV-Soc and Soc-PA are separately arrayed on different capsid of bacteriophage nanoparticle, and the immunogenic composition comprises a 1:1 mixture of bacteriophage nanoparticles separately displaying F1mutV-Soc and Soc-PA.

In some embodiment, bivalent (dual) anthrax-plague vaccine may be developed from the above described bacteriophage nanoparticles arrayed with above described Soc fusion proteins. In some embodiments, an immunization dosage of an immunogenic composition comprising one or more bacteriophage nanoparticles arrayed with one or more above described Soc fusion proteins on capsid surface of each of the one or more bacteriophage nanoparticles is administered to a subject in need thereof. The one or more Soc fusion proteins may be a Soc fused to an antigen selected from the group consisting of a mutated F1 antigen from Yersinia pestis, a V antigen from Yersinia pestis, a protective antigen (PA) from B. anthracis, and/or a combination thereof. The bacteriophage nanoparticles arrayed with all three antigens may be administered to a subject without adjuvant. The immunogenic composition is able to elicit immune response in the subject against anthrax and plague pathogens.

Vaccination

An immunization dosage of immunogenic compositions described above may be administered to a subject in need thereof by a variety of routes. For example, an immunization dosage of the immunogenic composition may be administered to a subject via parenteral routes. An immunization dosage of the immunogenic composition may be administered to a subject via intranasal route. An immunization dosage of the immunogenic composition may be administered to a subject subcutaneous injection, intramuscular injection, intravenous injection, inhalation, transdermal routes, or other routes. The immunogenic composition may be further administered to a subject twice during a period of time. A subject receiving the above described immunogenic composition may be a human and a non-human animal, such as mouse, rat, rabbit, nonhuman primate, etc.

In determining an effective amount, the dose of a vaccine, a number of factors are considered by the attending diagnostician, including, but not limited to: the type of a vaccine to be administered; the subject's weight, age, and general health; the response of the individual subject; the mode of administration; the dose regimen selected; the use of other concomitant medication; and other relevant circumstances.

The specific dose administered may be determined by particular circumstances surrounding each situation. These circumstances can include: the route of administration, the prior medical history of the recipient, the symptom being treated, the severity of the symptom being treated, and the age of the recipient. The recipient subject's attending physician should determine the therapeutic dose administered in light of the relevant circumstances.

All documents, patents, journal articles and other materials cited in the present application are incorporated herein by reference.

The many features and advantages of the invention are apparent from the detailed specification, and thus, it is intended by the appended claims to cover all such features and advantages of the invention which fall within the true spirit and scope of the invention. Further, since numerous modifications and variations will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation illustrated and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.

The disclosed invention is further defined in the following Examples. It should be understood that these Examples are given by way of illustration only. From the above discussion and these Examples, one skilled in the art can ascertain the essential characteristics of embodiments of the disclosed invention. Without departing from the spirit and scope thereof, one skilled in the art can make various changes and modifications of the invention to adapt it to various usages and conditions. All publications, including patents and non-patent literature, referred to in this specification are expressly incorporated by reference herein.

EXAMPLES Example 1 Construction of an Anthrax-Plague Triple Antigen

To create a bivalent anthrax-plague vaccine, we fused in-frame the coding sequences corresponding to F1mut antigen (SEQ ID NO: 1), V antigen (SEQ ID NO: 2), and PA (SEQ ID NO: 3) are fused in-frame as shown in FIG. 2A, resulting in F1mutV-PA triple antigen (SEQ ID NO: 4). As an example, the coding sequence for F1mutV is set forth in SEQ ID NO: 5, and the coding sequence for PA is set forth in SEQ ID NO: 6.

The F1mutV-PA protein (SEQ ID NO: 4) was expressed in Escherichia coli BL21-codon plus (DE3)-RIPL cells and purified from the soluble fraction at the yield of 5-10 mg/L. Remarkably, the 139 kDa F1mutV-PA protein consisting of seven domains belonging to three different proteins (FIG. 2B) was soluble and existed mainly as a monomer in solution as determined from the elution profile following size-exclusion chromatography (FIG. 11). FIG. 11 is a graph showing purification of F1mut1-PA according to one embodiment of the present invention. Elution profile of F1mut1-V by size-exclusion chromatography on a Hi-load 16/60 Superdex 200 column. The inset shows the purity of F1mut1-PA as analyzed by SDS-PAGE and Coomassie blue staining of the pooled peak fractions.

A series of quantitative biochemical analyses were performed to verify the functionality of F1mutV-PA. FIG. 2C illustrates the binding of F1mutV-PA to PA receptor, CMG2, according to one embodiment of the present invention. The PA or F1mutV-PA proteins were incubated with increasing amounts of CMG2 and interactions between the PA proteins and CMG2 were analyzed by Native-PAGE. PA-CMG2 and F1mutV-PA-CMG2 complexes are marked with light arrows. PA-CMG2 and F1mutV-PA-CMG2 complexes are marked with light arrows. PA and F1mutV-PA are marked with black arrows. FIG. 2D illustrates furin cleavage of F1mutV-PA according to one embodiment of the present invention. The recombinant PA or F1mutV-PA proteins were treated with increasing amounts of furin and cleavage products were analyzed by SDS-PAGE and Coomassie blue staining. Positions of the PA and F1mutV-PA bands are marked with light arrows and the positions of the PA63, PA20, and F1mutV-PA20 bands are marked with dark arrows. FIG. 2E illustrates the binding of F1mutV-PA to N-terminal domain of lethal factor (LFn) according to one embodiment of the present invention. The PA and F1mutV-PA proteins were first treated with furin to release PA63 and then incubated with increasing amounts of LFn. Interactions between the PA63 heptamer/octamer and LFn were analyzed by Native-PAGE. The PA63-LFn complexes are marked with braces. The SDS-PAGE and native gels were stained with Coomassie blue R-250 and Coomassie blue G-250, respectively.

First, as shown in FIG. 2C, F1mutV-PA bound to the soluble external domain of CMG2 equivalently as the rPA at different ratios of F1mutV-PA:CMG2, generating a high-molecular weight (MW) complex (FIG. 2C, light arrows). Second, as shown in FIG. 2D, F1mut-PA and rPA had similar sensitivity to various concentrations of furin. Whereas rPA is cleaved to PA63 and PA20, F1mutV-PA is cleaved to 76 kDa F1mutV-PA20 and PA63. Third, as shown in FIG. 2E, as in the case of the rPA, the PA63 generated by cleavage of F1mutV-PA bound to LFn (N-terminal PA-binding domain of LF), resulting in the formation of PA63-LFn complexes. Collectively, these results demonstrated that the biochemical properties of the fusion protein F1mutV-PA remained similar to rPA.

Example 2

Display of T4phage Nanoparticles with F1mut-V and PA

The 120×86 nm bacteriophage T4 capsid provides a nanoplatform for symmetrical arraying of antigens on the surface as fusion proteins of the capsid protein, Soc. Previous studies showed that antigens fused to phage RB49 Soc (a close relative of T4 phage) are more soluble than the same fused to T4 Soc and could be efficiently displayed on the capsid.²³ In this example, three recombinants using the RB49 Soc were constructed: F1mutV-Soc-PA (148 kDa), F1mutV-Soc (66 kDa), and Soc-PA (93 kDa). These three recombinants were assembled on T4 nanoparticles in three different ways: i) display of F1mutV-Soc-PA, ii) display of F1mutVSoc and Soc-PA on the same capsid, and iii) a 1:1 mixture of T4 phage particles separately displayed with F1mutV-Soc or Soc-PA. Of these, the latter produced particles with the highest copy number of the antigens per capsid whereas F1mutV-Soc-PA produced particles with the least copy number (data not shown). Hence this formulation, T4-F1mutV-Soc/Soc-PA (abbreviated as T4-F1mutV/PA) was used for all immunization experiments (see below) disclosed herein.

FIG. 12 is a graph showing purification of Soc-PA according to one embodiment of the present invention. The Soc-PA recombinant protein was purified from the cell-free lysates by HisTrap affinity chromatography followed by Hiload 16/60 Superdex 200 gel filtration. The inset shows the purity of Soc-PA after SDSPAGE and Coomassie blue staining of the pooled peak fractions.

FIGS. 3A, 3B, 3C, and 3D illustrate the display of F1mutV-Soc and Soc-PA on Hoc-Soc-T4 phage according to one embodiment of the present invention. Approximately 2×10¹⁰ Hoc-Soc-T4 phage particles were incubated at the indicated ratios of F1mutV-Soc or Soc-PA molecules to capsid binding sites. The control lane is the Hoc-Soc-phage used in the experiment. F1mutV-Soc (FIG. 3A) and Soc-PA (FIG. 3B) bands, which are not present in the phage control, are labeled with light arrows. FIG. 3C and FIG. 3D show saturation binding curves of F1mutV-Soc (FIG. 3C) and Soc-PA (FIG. 3D). The density volumes of bound F1mutV-Soc (FIG. 3A) and Soc-PA (FIG. 3B) from SDS-PAGE were determined by laser densitometry and normalized to that of gp23* present in the respective lane. The unbound F1mutV-Soc and Soc-PA were quantified in separate gels. The copy numbers were determined in reference to gp23* (930 copies per capsid). The data were plotted as one site saturation ligand binding curve and the calculated binding parameters are shown. Kd, apparent binding constant; B_(max), maximum copy number per phage particle.

To optimize the copy number for immunization experiments, the cesium chloride (CsCl) gradient-purified Hoc-Soc-phage particles were incubated with the purified F1mutV-Soc or Soc-PA proteins at different ratios of antigen molecules to Soc binding sites (FIGS. 3A, 3B, 3C, and 3D). Binding increased with increasing ratio, reaching saturation at ˜20:1 (FIGS. 3A and 3B). The copy number of antigens displayed per capsid (B_(max)) is 657 for the 66-kDa F1mutV-Soc and 370 for the 93-kDa Soc-PA, and the apparent binding constants (K_(d)) were 298 nM and 737 nM, respectively (FIGS. 3C and 3D). Since there are 870 Soc binding sites per capsid, the percent occupancy is 75% for F1mutV-Soc and 42% for Soc-PA. These represent high occupancy considering that the large size of the antigens is expected to cause some steric hindrance that prevents saturation of the Soc binding sites.

Example 3 The Soluble and T4 Nanoparticle Anthrax-Plague Dual Vaccines are Highly Immunogenic in Mice

FIGS. 4A through 4E show that the F1mutV-protective antigen (PA) triple antigen and T4nanoparticle anthrax-plague dual vaccine T4-F1mutV/PA are highly immunogenic in mice according to embodiments of the present invention. FIG. 4A shows vaccine formulations used in various immunized mouse groups according to one embodiment. The protein combinations used for each group are shown. FIG. 4B illustrates the immunization scheme according to one embodiment. In this embodiment, Mice (n=10) were immunized (intramuscular) on days 0 and 21. Sera were collected on days 0 and 35 for antibody analysis. Animals were challenged with lethal toxin (LeTx) on day 42 followed by Yersinia pestis CO92 on day 75. FIG. 4C is a graph illustrating F1V-specific antibody titers according to one embodiment. FIG. 4D is a graph showing PA-specific antibody titers according to one embodiment. FIG. 4E is a graph showing LeTx-neutralizing antibody titers according to one embodiment. Error bars represent SD. “*,” “***,” and “****” denote p<0.05, p<0.001, and p<0.0001, respectively (ANOVA).

As shown in FIG. 4A, in this example, Balb/c mice (n=10/group) were immunized by the intramuscular (i.m.) route with equivalent amounts (25 j g) of soluble (F1mutV-PA) or T4 nanoparticle displayed (T4-F1mutV/PA) immunogens and were boosted once on day 21. Mice immunized with PA alone, F1mutV alone, or a mixture of F1mutV and PA (F1mutV+PA) served as control groups (FIG. 4A and FIG. 4B). The latter group allowed assessment of our dual vaccine formulations relative to a simple mixture of the two antigens.

All of the F1mutV immunogens elicited high and comparable levels of F1mutV specific IgG antibodies, up to an end point titer of ˜3×10⁶ (FIG. 4C). The PA antigens similarly elicited high antibody titers; however, significant differences were observed among the groups (FIG. 4D). The T4-displayed F1mutV/PA induced the highest PA-specific IgG titers followed by F1mutV-PA (p<0.001). Both these antigens induced significantly higher titers than did PA alone or F1mutV+PA (FIG. 4D). The naïve animals, as expected, showed no antibodies to either PA or F1mutV (FIGS. 3D and 4D). Similarly, the animals immunized with PA alone had no F1mutV-specific antibodies and vice-a-versa (FIGS. 3D and 4D).

A toxin neutralization assay (TNA) was performed to determine LeTx neutralizing activity by anti-PA antibodies present in the sera of the immunized mice. Previous studies demonstrated that the levels of LeTx neutralizing antibodies correlated with protection against inhalational B. anthracis challenge.³⁶ All of the groups immunized with the PA antigen demonstrated strong LeTx neutralization titers (FIG. 4E). The naïve animals (PBS group) or the F1mutV-immunized animals, as expected, were negative for toxin neutralization.

FIGS. 5A through 5D illustrates subtype specificity of antibodies elicited by F1mutV-protective antigen (PA) triple antigen and T4nanoparticle anthrax-plague dual vaccine T4-F1mutV/PA in mice, according to one embodiment of the present invention. FIG. 5A is a graph illustrating F1V-specific IgG1 antibody titers elicited by F1mutV-protective antigen (PA) triple antigen and T4-F1mutV/PA in mice. FIG. 5B is a graph illustrating F1V-specific IgG2a antibody titers elicited by F1mutV-protective antigen (PA) triple antigen and T4-F1mutV/PA in mice. FIG. 5C is a graph illustrating PA-specific IgG1 antibody titers elicited by F1mutV-protective antigen (PA) triple antigen and T4-F1mutV/PA in mice. FIG. 5D is a graph illustrating PA-specific IgG2a antibody titers elicited by F1mutV-protective antigen (PA) triple antigen and T4-F1mutV/PA in mice. In this example, Mice were immunized (i.m.) according to FIGS. 4A and 4B. Sera were collected according to FIG. 4B and analyzed by ELISA. “*”, “**”, “***”, and “****” denote p<0.05, p<0.01, p<0.001, and p<0.0001, respectively (ANOVA).

Stimulation of both arms of the immune system, humoral (TH2) and cellular (TH1), is essential for protection against Y. pestis infection³⁷ and probably also against B. anthracis infection.³⁸ With this in mind, the IgG subclass of the induced antibodies was determined by ELISA (FIG. 5). In mice, IgG2a titer represents TH1 response whereas IgG1 reflects the TH2 response. The data showed that the T4-displayed F1mutV/PA group elicited the highest levels of IgG2a antibodies against F1mutV or PA (p<0.0001) whereas the rest of the groups induced poor IgG2a responses (FIGS. 5B and 5D). On the other hand, although significant differences were observed, the variation of IgG1 antibody levels was relatively small among the groups (FIGS. 5A and 5C). These results indicated that the T4 nanoparticle-delivered antigens stimulated strong TH1 cellular as well as TH2 humoral responses, whereas the soluble antigens (adjuvanted with Alhydrogel®) showed a bias towards TH2 responses, as has been generally observed with many subunit vaccines.³⁹ Notably however, the largest among the soluble antigens, the 139-kDa F1mutV-PA triple antigen elicited significantly greater IgG2a against both F1V and PA antigens, (FIGS. 5B and 5D) when compared to the rest of the groups. Thus, the triple antigen F1mutV-PA is a more potent immunogen when compared to the individual antigens or a simple mixture.

Example 4

The Dual Vaccines Protect Mice Against Challenges with LeTx and Y. pestis CO92

Since the goal was to assess protection against both inhalation anthrax and pneumonic plague, it became imperative to establish appropriate challenge models. In previous reports on dual anthrax-plague vaccines (mixture of PA, F1, and V),⁴⁰⁻⁴³ groups of animals were immunized with the same formulation but challenged separately with either B. anthracis (intratracheal administration of spores prepared from the nonencapsulated toxigenic Sterne strain⁴⁰ or subcutaneous challenge⁴¹) or Y. pestis (intraperitoneal⁴⁰ or subcutaneous⁴¹⁴³ injection). However, this model would not provide an accurate assessment of dual protection because the animals were not exposed to both the agents. Therefore, two new challenge models are developed and disclosed herein; a sequential dual challenge model in which the animals were first exposed to one agent and the survivors were then challenged with the second agent, and a simultaneous dual challenge model in which the animals were exposed to both the threat agents at the same time.

In this example Balb/c mice and Brown Norway rats were chosen because both these animal strains are highly susceptible to LeTx and Y. pestis bacterial challenge and the protection outcomes provide good benchmarks for evaluation of vaccine efficacy.⁴⁴⁻⁴⁶ Since the most virulent form of Y. pestisis the aerosolized form,³ intranasal (i.n.) challenge was used to evaluate vaccine efficacy.

FIG. 6A is a graph illustrating survival of the mice against anthrax toxin and plague sequential challenge according to one embodiment of the present invention. Mice (n=10/group) were immunized (i.m.) according to FIG. 4b and challenged with 1 LD₁₀₀ LeTx (i.p.) on day 42 post-immunization, followed by i.n. challenge with 400 LD₅₀ Y. pestis CO92 on day 75 post-immunization. FIG. 6B is a graph illustrating survival of the mice against anthrax toxin and plague simultaneous challenge according to one embodiment of the present invention. Mice (n=8/group) were immunized (i.m.) with F1mutV+PA, F1mutV-PA or the T4-displayed F1mutV/PA. On day 44 postimmunization, mice were simultaneously challenged with 200 LD₅₀ Y. pestis (i.n.) and 1 LD₁₀₀ LeTx (i.p.). FIG. 6C are in vivo imaging of infected mice according to one embodiment. In Luciferase expression by Y. pestis in representative mice from the F1mutV-PA and the T4-displayed F1mutV/PA groups on day 3 post-infection is shown. The PBS control group used for imaging here was challenged with Y. pestis alone to minimize any interference from LeTx. Note that death of animals challenged with Y. pestis alone occurred in 4 days, whereas it occurred in 2 days when LeTx was included in the challenge as the toxin leads to early animal lethality (FIG. 6B).

For sequential challenge, mice were immunized as per the scheme shown in FIG. 4B and injected intraperitoneally (i.p.) with 1 LD₁₀₀ of LeTx (1:1 mixture of PA and LF, 100 μg each) two weeks after the boost. The immunized groups were 80-100% protected against LeTx challenge whereas 90% of the naïve group mice died within two days of toxin challenge. The T4-displayed F1mutV/PA group showed 80% survival whereas the PA, F1mutV-PA, and F1mutV+PA groups were 100% protected (FIG. 6A). Thirty-three days later, the surviving animals were challenged with 400 LD50 of Y. pestis CO92 by intranasal (i.n.) administration. The naïve mice and the F1mutV-immunized mice were used as negative and positive controls, respectively. The LeTx-challenged PA group provided another (negative) control. Dual vaccine groups showed 80-100% protection whereas the naïve and PA-immunized animals showed 100% death within 4 days post-Y. pestis CO92 challenge (FIG. 6A). The survival rates for individual groups were 100% for the T4-displayed F1mutV/PA group (no death), 90% for the F1mutV-PA group (one of ten mice died), and 80% for the F1mutV+PA group (two of ten mice died). As reported previously,²³ the control F1mutV-immunized mice were fully protected.

To test the potential protective ability of the vaccines in a simultaneous exposure model to both B. anthracis and Y. pestis, mice were challenged with LeTx and Y. pestis CO92 at the same time. Mice (n=8) were immunized twice as per the same scheme (FIG. 4B) and challenged with both LeTx (1 LD₁₀₀, i.p. administration) and Y. pestis CO92 (200 LD₅₀, i.n. administration) twenty-three days after the boost (day 44 postimmunization). Because of the simultaneous administration of two agents in mice, the challenge dose of Y. pestis to 200 LD₅₀ from 400 LD₅₀ is reduced (FIG. 6A). As shown in FIG. 6B, all the PBS control mice died within 2 days of challenge. The F1mutVPA vaccine provided 100% protection (8 out of 8 mice), while the T4-displayed F1mutV/PA and F1mutV+PA mixture provided 88% (7 out of 8 mice) and 75% (6 out of 8 mice) protection, respectively. Furthermore, the survivors showed complete clearing of Y. pestis bacteria by 3 days post-challenge (FIG. 6C). The Y. pestis CO92 strain used in the challenge experiment contained a luciferase expression cassette for imaging the bacteria in vivo in real time.⁴⁴ The immunized animals were negative for bioluminescence, whereas the PBS control mice showed bacterial dissemination throughout the body (FIG. 6C).

The above data sets demonstrated that both the soluble and T4 nanoparticle anthrax-plague vaccines were highly immunogenic in the mouse model and conferred near complete protection upon sequential double challenge or simultaneous double challenge with LeTx and Y. pestis CO92.

Example 5

The Dual Vaccines Provide Complete Protection Against Both LeTx and Y. pestis CO92 in Brown Norway Rats

FIGS. 7A through 7E illustrate that the F1mutV-protective antigen (PA) triple antigen and T4-displayed F1mutV/PA are highly immunogenic in rats. FIG. 7A is a table showing vaccine formulations used in various immunized rat groups. FIG. 7B shows immunization scheme using the disclosed proteins combinations for each group for rat studies. Rats (n=9) were immunized (i.m.) on day 0 and 21. Sera were collected on day 0 and 35 for antibody analysis. Animals were challenged with Y. pestis (i.n.) on day 42 followed by LeTx (i.v.) on day 111. FIG. 7C is a graph showing F1V-specific antibody (total IgG) titers. FIG. 7D is a graph showing PA-specific antibody (total IgG) titers. FIG. 7E is a graph showing LeTx neutralizing antibody titers. Error bars represent standard deviation (SD). “**” denotes p<0.01 (ANOVA).

Rat, the natural host of Y. pestis through its infection by rat fleas, is one of the most reliable models to assess the protective efficacy of vaccines against plague.⁴⁵ To further evaluate our dual vaccines, Brown Norway rats (n=9) were immunized and challenged using the scheme shown in FIGS. 7A and 7B. As in mice, the immunogens induced high levels of total antigen-specific IgG titers, up to ˜3×10⁶ (FIG. 7C). However, the F1mutV-PA and T4-displayed F1mutV/PA immunogens induced significantly lower levels of anti-F1V IgG when compared to F1mutV and F1mutV+PA antigens (p<0.01; FIG. 7C), although the anti-PA IgG levels were comparable among all the groups (FIG. 7D). Consistent with the latter, all the PA groups generated comparable LeTx neutralizing antibodies (EC₅₀ of 4,300 to 8,500) (FIG. 7E). The naïve animals, as expected, were negative for the antigen-specific or LeTx-neutralizing antibodies. Similarly, the PA-alone animals were negative for F1mutV antibodies and the F1mutV-alone animals were negative for PA and LeTx-neutralizing antibodies.

FIG. 13A is a graph showing F1V-specific IgG1 antibody titers in rats according to one embodiment of the present invention. FIG. 13B is a graph showing F1V-specific IgG2a antibody titers in rats according to one embodiment of the present invention. FIG. 13C is a graph showing PA-specific IgG1 antibody titers in rats according to one embodiment of the present invention. FIG. 13D is a graph showing PA-specific IgG2a antibody titers in rats according to one embodiment of the present invention. Animals were immunized (i.m.) according to FIGS. 7A and 7B. Sera were collected according to FIG. 7B and analyzed by ELISA. “*”, “**”, “***”, and “****” denote p<0.05, p<0.01, p<0.001, and p<0.0001, respectively (ANOVA).

As shown in FIGS. 13A through 13 D, the IgG subclass specificity of the antibodies induced in rats followed similar trends as in mice. The T4 nanoparticle-displayed F1mutV/PA induced similar levels of both IgG1 and IgG2a antibodies against both F1mutV and PA immunogens (FIGS. 13A and 13B) whereas the soluble antigens showed a bias towards IgG1. The bias was more apparent in the case of anti-PA (FIGS. 13C and 13D) than in the case of anti-F1mutV.

FIGS. 8A through 8C illustrate that the bivalent anthrax-plague vaccine provides complete protection against both lethal toxin (LeTx) and Yersinia pestis CO92 in Brown Norway rats. FIG. 8A is a graph showing survival of the rats against anthrax toxin and plague sequential challenge. Rat (n=9) were challenged intranasally with 400 LD50 Y. pestis CO92, followed by i.v. intravenous injection with 1 LD100 LeTx. FIG. 8B is a set of in vivo imaging of infection. Luciferase expression by Y. pestis in representative rats from the naïve control (PBS-immunized animals) and the T4-F1mutV/PA-immunized groups two days after Y. pestis CO92 challenge is shown. FIG. 8C is a graph showing survival of the rats against anthrax LeTx and plague simultaneous challenge. Rats (n=6) were immunized according to FIG. 7B and challenged simultaneously with 1×LD100 (i.v.) of LeTx and 400 LD50 Y. pestis CO92 (i.n.).

The protective efficacy of the dual vaccines in Brown Norway rats was first tested by the sequential dual challenge model (FIG. 8A). The animals were first subjected to i.n. challenge with 400 LD₅₀ of Y. pestis CO92. All the F1mutV-immunized rats were completely protected whereas all the rats in the naïve group died within 2 days postchallenge. The clearance of Y. pestis CO92 from the rats was also monitored through live imaging of the in vivo expressed luciferase (FIG. 8B). The data showed that 2 days post-challenge with Y. pestis, all immunized rats cleared Y. pestis CO92 as indicated by the lack of a detectable luciferase signal, while all control rats had strong luciferase signals throughout the body. The surviving rats were then further challenged with 1 LD₁₀₀ of LeTx (7.5 μg each of PA and LF) by intravenous (i.v.) injection on day 70 post-Y. pestis CO92 challenge. All immunized rats survived (FIG. 8A), but rats in the F1mutV group (negative control) as expected died within 2 h of the LeTx challenge.

In an independent experiment, rats (n=6) were simultaneously challenged with both LeTx (1 LD₁₀₀, i.v.) and Y. pestis CO92 (400 LD₅₀, i.n.). Both the dual vaccines showed 100% protection (FIG. 8C). At the end of the study, various organs (lungs, liver, and the spleen) were examined for the presence of Y. pestis by plate count, and no viable bacteria were detected.

Taken together, these sets of data demonstrated that although the antibody profiles to F1mutV-PA and the T4-displayed F1mutV/PA in rats were slightly different from the mouse model, the antibodies provided complete protection against sequential or simultaneous LeTx and Y. pestis CO92 challenges.

Example 6 Immunogenicity and Protective Efficacy of Dual Vaccines in a Rabbit Model

Rodents are very sensitive to infection by B. anthracis bacteria that produce polyglutamic acid capsule. They succumb to encapsulated B. anthracis infection even if these bacteria do not produce anthrax toxin.⁴⁶ Thus, to use rodents for testing efficacy of vaccines which target anthrax toxins, lethal dose toxin challenge models are preferred. Rabbits are a better model to determine protective efficacy of anthrax vaccines against encapsulated toxigenic B. anthracis as inhalation anthrax in these animals shows remarkably similar pathology to that observed in humans.⁴⁷ FIGS. 9A through 9G show that the triple antigen vaccines disclosed herein provide complete protection in the New Zealand White rabbit model of inhalation anthrax. FIG. 9A is a table showing vaccine formulations used in various groups in this example. Rabbits (n=10 for groups 1 and 2, and n=6 for groups 3 and 4, equal numbers of males and females) were vaccinated (i.m.) with the indicated antigens. FIG. 9B is an immunization scheme for rabbit study in this example. FIG. 9C is a graph showing F1V-specific antibody (total IgG) titers on day 20 in this example. Error bars represent standard deviation (SD). FIG. 9D is a graph showing F1V-specific antibody (total IgG) titers on day 42 in this example. Error bars represent standard deviation (SD). FIG. 9E is a graph showing protective antigen (PA)-specific antibody (total IgG) titers. Titers for bleeds on days 0, 12, 20, and 42 are shown. FIG. 9F is a graph showing LeTx neutralizing antibody titer. All animals immunized with PA induced robust neutralization antibody and no significant difference was observed among the PA-immunized groups. FIG. 9G is a graph showing survival of the rabbits challenged with 200 LD50 of aerosolized B. anthracis Ames spores. Error bars represent standard deviation (SD) of the mean. “**” and “***” denote p<0.01 and p<0.001, respectively (ANOVA).

As shown in FIG. 9A and FIG. 9B, rabbits (n=10 for groups 1 and 2, and n=6 for groups 3 and 4, equal numbers of males and females) were primed on day 0 and boosted on day 14 by i.m. injections of vaccine formations. Sera were collected on days 0, 12, 20, and 42 (FIG. 9B) and subjected to immunological analyses. The data showed that both the soluble and T4 nanoparticle vaccines induced high levels of anti-PA antibodies as well as LeTx neutralizing antibodies at day 20 (FIGS. 9E and 9F). Importantly, the T4 nanoparticle vaccine elicited the highest antibody levels (p<0.001; FIG. 9E), although the titer dropped by 30% by day 42 (p<0.01; FIG. 9E).

The rabbits also induced high levels of anti-F1mutV antibodies. At day 20, six days after the boost, the end point titers were in the range of 0.3-1.6×10⁶ (FIG. 9C). While the total IgG levels were comparable among groups, they were more durable in the T4 vaccine group than in the soluble vaccine group, as shown by 11% drop on day 42 in the F1mutV-PA group and no significant drop in the T4-F1mutV/PA group (p<0.01; FIG. 9D).

Rabbits were challenged one week after the boost with 200 LD₅₀ of aerosolized B. anthracis Ames spores. All the naïve control rabbits succumbed to the anthrax disease 2-4 days post-infection, while all the dual vaccine immunized rabbits were completely protected (FIG. 9G). Between the challenge day and the end of the study (days 28 to 42), vaccinated animals from Groups 1, 2, and 3 continued to show an increase in the body weight, while control animals showed weight loss as well as body temperature changes before death (FIGS. 14A through 14 D). FIGS. 14A through 14 D show body weight changes body weight changes in male (FIG. 14A) and female (FIG. 14B) rabbits, and body temperature changes in male (FIG. 14C) and female (FIG. 14D) rabbits after B. anthracis challenge (200 LD50, aerosol) according to one embodiment of the present invention. Animals were immunized (i.m.) according to FIG. 9A and FIG. 9B and challenged (aerosol) with 200 LD₅₀ B. anthracis two weeks after last immunization. The rabbits were monitored daily for body weight and body temperature.

In further experiments, blood samples for bacteremia were drawn before the challenge on day 27 (baseline), and on days 29-33 (1-5 days post-exposure) and day 42. Tables 1 and 2 shows a summary of challenge experiments and qualitative bacteremia in blood. As shown in Table 2, vaccinated animals (Groups 1-2) never developed bacteremia whereas all unvaccinated control animals (Group 3) became positive for bacteremia before they succumbed to the disease. To determine the bacterial load of internal organs, post-mortem collection of specimens was performed after scheduled euthanasia of surviving animals on study day 42 (Groups 1 and 2) or after animals died due to the anthrax exposure (Group 3). Table 3 shows individual chart of bacterial load of tissue samples. All vaccinated animals from Groups 1 and 2 had cleared the agent from the lungs and did not have any bacteria in the brain, liver, or spleen. In contrast, tissue samples collected from unvaccinated control animals (Group 3) had very high bacterial titers indicative of systemic anthrax infection. In increasing order, the brain titer average was 5×10⁶ CFU/g, the liver average was 3×10⁷ CFU/g, and the highest average titer of 5×10⁸ CFU/g was obtained for lung and spleen samples. Gross necropsy and histological analyses were consistent with these data.

The above sets of data demonstrated that both our soluble and T4 nanoparticle dual anthrax-plague vaccines provided complete protection in rabbits against aerosolized B. anthracis Ames spore challenge.

TABLE 1 Summary of Challenge Experiments Challenge Challenge dose Animal models agent (route) Schedule Mouse sequential LeTx and 1 LD₁₀₀ of LeTx (i.p.) Challenge with LeTx on day challenge Y. pestis CO92 and 400 LD₅₀ of zero followed by Y. pestis Y. pestis (i.n.) challenge on day 33 simultaneous LeTx and 1 LD₁₀₀ of LeTx (i.p.) Simultaneous challenge with challenge Y. pestis CO92 and 200 LD₅₀ of Y. LeTx and Y. pestis on day pestis (i.n.) zero Rat sequential LeTx and 400 LD₅₀ of Y. pestis Challenge with Y. pestis on challenge Y. pestis CO92 (i.n.) and 1 LD₁₀₀ of day zero followed by LeTx LeTx (i.v.) challenge on day 70 simultaneous LeTx and 1 LD₁₀₀ of LeTx (i.v.) Simultaneous challenge challenge Y. pestis CO92 and 400 LD₅₀ of with LeTx and Y. pestis (i.n.) Y. pestis on day zero Rabbit B. anthracis 200 LD₅₀ of challenge with aerosolized Ames spores aerosolized B. anthracis Ames B. anthracis Ames spores on day zero spores (i.n.)

TABLE 2 Summary of Qualitative Bacteremia in Blood Animal ID Day 27 Day 29 Day 30 Day 31 Day 32 Day 33 Day 42 Group 1 2M14117 − − − − − − F1mutV-PA 2M14122 − − − − − − (Male) 2M14120 − − − − − − 2M14106 − − − − − − 2M14111 − − − − − − Group 1 2F14123 − − − − − − F1mutV-PA 2F14124 − − − − − − (Female) 2F14129 − − − − − − 2F141134 − − − − − − 2F14136 − − − − − − Group 2 3M14110 − − − − − − PA 3M14115 − − − − − − (Male) 3M14118 − − − − − − Group 2 3F14127 − − − − − − PA 3F14139 − − − − − − (Female) 3F14141 − − − − − − Group 3 4M14107 − − + + PBS control 4M14112 − − + (Male) 4M14131 − − − + + Group 3 4F14105 − − − + PBS control 4F14125 − − + + (Female) 4F14140 − − +

TABLE 3 Individual Chart of Bacterial Load of Tissue Samples Brain Liver Lung Spleen Animal ID (CFU/g) (CFU/g) (CFU/g) (CFU/g) Group 1 2M 14117 0.0E+00 00E+00 0.0E+00 0.0E+00 F1mutV- 2M 14122 0.0E+00 0.0E+00 0.0E+00 0.0E+00 PA 2M 14120 0.0E+00 0.0E+00 0.0E+00 0.0E+00 (Male) 2M 14106 0.0E+00 0.0E+00 0.0E+00 0.0E+00 2M 14111 0.0E+00 0.0E+00 0.0E+00 0.0E+00 Group 1  2F 14123 0.0E+00 00E+00 0.0E+00 0.0E+00 F1mutV-  2F 14129 0.0E+00 0.0E+00 0.0E+00 0.0E+00 PA  2F 14124 0.0E+00 0.0E+00 0.0E+00 0.0E+00 (Female)  2F 14136 0.0E+00 0.0E+00 0.0E+00 0.0E+00  2F 14134 0.0E+00 0.0E+00 0.0E+00 0.0E+00 Group 2 3M 14110 0.0E+00 0.0E+00 0.0E+00 0.0E+00 PA 3M 14115 0.0E+00 0.0E+00 0.0E+00 0.0E+00 (Male) 3M 14118 0.0E+00 0.0E+00 0.0E+00 0.0E+00 Group 2  3F 14127 0.0E+00 0.0E+00 0.0E+00 0.0E+00 PA  3F 14141 0.0E+00 0.0E+00 0.0E+00 0.0E+00 (Female)  3F 14139 0.0E+00 0.0E+00 0.0E+00 0.0E+00 Group 3 4M 14112 6.4E+06 7.5E+06 9.9E+06 7.9E+06 PBS 4M 14107 9.8E+05 2.9E+06 9.1E+08 1.4E+00 control 4M 14105 2.0E+0.6 5.6E+07 1.4E+09 2.5E+09 (Male) Group 3  4F 14131 1.0E+07 0.0E+00 4.6E+06 1.9E+06 PBS  4F 14125 2.4E+06 3.9E+07 8.0E+08 2.7E+08 control  4F 14140 7.9E+06 4.9E+07 4.8E+07 6.2E+06 (Female)

CONCLUSIONS

Since the deadly anthrax attacks of 2001, stockpiling of recombinant plague and anthrax vaccines has been a national priority. However, no candidate vaccines have yet been able to meet the licensing requirements. A single vaccine, rather than two different vaccines, which can protect against both Tier-1 bioterror pathogens, B. anthracis and Y. pestis, would greatly accelerate this effort. We report here two such vaccines, a triple fusion protein (F1mutV-PA) that incorporates all three key antigens, F1 and V from Y. pestis and PA from B. anthracis, and a T4 phage nanoparticle with all three antigens arrayed on the virus capsid (T4-F1mutV/PA). These candidate vaccines retained the functionality and immunogenicity of the antigens and elicited robust and protective immune responses in three animal models, namely mouse, rat, and rabbit.

There have been several previous studies on developing a dual anthrax-plague vaccine, all involving a simple mixture of F1, V, and PA proteins.⁴⁰⁻⁴² Both synergy and interference in antibody production have been reported when the antigens were mixed and none of the candidate vaccines were tested for efficacy against both the biothreat agents.⁴⁰⁻⁴² Our studies showed no evidence of antigen interference occurring with our dual vaccines in three different animal models. Although enhancement was observed in the case of F1mutV-PA, which elicited significantly higher levels of PA-specific IgG than PA alone or F1mutV+PA mixture, this was only observed in the mouse model and not in the rat and rabbit models.

Disclosed T4 nanoparticle vaccine elicited robust and balanced humoral (TH1) and cellmediated (TH2) immune responses. This was observed with both the anthrax and plague antigen-specific responses in two animal models, as well as in our previous studies.²³ The soluble immunogens on the other hand showed a bias towards TH2 responses, as has been generally observed with subunit vaccines.^(23,48) Presumably, the nanoparticle character of the T4 phage allows for its efficient uptake by the antigen presenting cells and crosspresentation to both MHC-I and MHC-II molecules, stimulating both the humoral and cellular arms of the immune system. Thus, T4 might represent a particularly useful platform for clearance of Y. pestis and B. anthracis bacteria.

Vaccine efficacy studies demonstrated that the disclosed dual vaccines are highly effective in protection against both anthrax and plague challenges. This has been determined in three different animal models using i) multiple challenge formats, including: sequential challenge and simultaneous challenge using lethal doses of both LeTx and Y. pestis CO92, ii) multiple routes of administration: intranasal, intraperitoneal, intravenous, and aerosol administration of Y. pestis CO92, LeTx, and B. anthracis Ames spores, respectively, iii) two of the best animal models available for inhalation anthrax (New Zealand white rabbit), and pneumonic plague (Brown Norway rat). These studies are the first to demonstrate protection of vaccinated animals against simultaneous administration of both anthrax and plague.

The recombinant F1mutV-PA vaccine is a soluble molecule and can be cost-effectively produced in E. coli. It can be adjuvanted with Alum or another licensed adjuvant using the already established processes in vaccine manufacturing. Indeed, F1mutV-PA adjuvanted with liposomes or Alum-liposomes mixture provided similarly robust immune responses and complete protection against both anthrax and plague.

The novel T4 nanoparticle platform has several useful features, as follows: i) unlike traditional vaccines, it does not require an external adjuvant and elicits robust humoral and cellular immune responses;^(23,32,49) ii) it is an extremely stable particle, suitable for storage, stockpiling, and deployment on a mass scale;²⁹ iii) it is a multivalent platform, allowing incorporation of additional antigens belonging to other biothreat or emerging pathogens;³⁰ iv) no adverse effects to vaccination have been observed in many preclinical studies performed in mouse,^(23,26,31,49) rat,²³ rabbit,⁵⁰ and rhesus macaque³² models, or in a human trial where T4 phage was given orally;⁵¹ and v) no pre-existing antibodies are present in humans.

Disclosed study represents a new approach to develop anthrax and plague vaccines. Both dual vaccines described here are strong candidates for stockpiling as part of our national preparedness against two of the deadliest bioterror threats, anthrax and plague.

Example 7 Methods Ethics Statement

This study was conducted in accordance with the Guide for the Care and Use of Laboratory Animals recommended by the National Institutes of Health. All animal experiments were performed according to the protocols approved by the Institutional Animal Care and Use Committees of the University of Texas Medical Branch, Galveston, Tex. (Office of Laboratory Animal Welfare assurance number: A3314-01), The Catholic University of America, Washington, D.C. (Office of Laboratory Animal Welfare assurance number: A4431-01), and Southern Research Institute (Study No: 13538.01.15; Birmingham, Ala.). This is not their assurance number.

Construction of Recombinant Plasmids

The E. coli expression vector pET28b (EMD Biosciences, Darmstadt, Germany) was used for recombinant plasmid construction. Plasmids pET-F1mutV and pET-F1mutVSoc were constructed in previous studies.^(23,25) In order to construct pET-F1mutV-PA, overlap polymerase chain reaction (PCR) was used with the primers listed below. Using previously constructed Soc fusion protein Soc-PA as a template,³⁰ the PA fragment was amplified such that the HindIII site (underlined) was destroyed and a short linker (5′-CTGCT-3′; boldfaced) was introduced towards the 5′ end of the HindIII Forward primer after the HindIII restriction site to keep the codon in frame.

HindIII Forward: (SEQ ID NO: 8) 5′-ACCCAAGCTT

GAAGTTAAACAGGAGAACCGG TTATT-3′ Upstream Reverse: (SEQ ID NO: 9) 5′-GTGATTAATAAAGCCTCTAATTCTAACAAA-3′ Downstream Forward: (SEQ ID NO: 10) 5′-TTTGTTAGAATTAGAGGCTTTATTAATCAC-3′ XhoI Reverse: (SEQ ID NO: 11) 5′-GCCCTCGAGTTATCCTATCTCATAGCCTTTTTTAG-3′

The PA fragment was then double-digested with HindIII/XhoI and cloned into pETF1mutV-Soc, cut with the same enzymes, to replace Soc. The resulting pET-F1mutV-PA contains the PA fragment fused in-frame to the C-terminus of F1mutV with a short linker (Glu-Ala-Ser-Ala) (SEQ ID NO: 12) in between. The pET-Soc-PA was constructed by replacing the F1mutV gene of pET-F1mutV-PA with Soc using the following primers, where the underlined sequences corresponded to the recognition sequences for the respective enzymes:

Soc NheI Forward: (SEQ ID NO: 13) 5′-GCATCCGCTAGCGGTGGTTATGTAAACATCAAA-3′ Soc HindlII Reverse: (SEQ ID NO: 14) 5′-CAGAAGCTTCACCACTTACTGGTGTAGGGGTAA AC-3′

Soc fragment was double-digested with NheI/HindIII and cloned into pET-F1mutV-PA, cut with the same enzymes, to replace F1mutV. The resulting pET-Soc-PA contains the Soc gene fused in-frame to the N-terminus of PA with a short linker (Glu-Ala-Ser-Ala) (SEQ ID NO: 12) in between. All constructs were confirmed by DNA sequencing.

Expression and Purification of Immunogens

PA and LF were purified as described previously.^(52,53) The E. coli BL21-codon plus (DE3)-RIPL cells (Agilent Technologies, Santa Clara, Calif.) harboring various recombinant plasmids constructed as above were induced with 1 mM Isopropyl β-D-1-thiogalactopyranoside (IPTG) for 2 h at 28° C. Cells were harvested and resuspended in binding buffer (50 mM Tris-HCl, pH 8, 300 mM NaCl, 20 mM imidazole) containing protease inhibitor cocktail (Roche, USA, Indianapolis, Ind.). Cells were lysed at 12.00 psi using a French press (Aminco, Urbana, Ill.) and the soluble fractions containing the His-tagged fusion proteins were isolated by centrifugation at 34,000×g for 20 min. Proteins were first subjected to purification by HisTrap column (AKTA-prime, GE Healthcare Bio-Sciences Corp., Piscataway, N.J.). Peak fractions containing the desired protein were further purified by gel-filtration on a HiLoad 16/60 Superdex 200 column (AKTA-FPLC, GE Healthcare Bio-Sciences Corp.) in a buffer containing 20 mM Tris-HCl, pH 8 and 100 mM NaCl. The purified proteins were quantified and stored at −80° C. until use. The Endosafe-PTS system (Charles River Laboratories International, Inc., Wilmington, Mass.) was used to determine levels of lipopolysaccharide (LPS) contamination in the purified recombinant proteins and LPS-free preparations were used for animal immunizations.

Biochemical Function of F1mutV-PA

The furin cleavage of F1mutV-PA was carried out by incubation of F1mutV-PA (SEQ ID NO: 4) with human furin (amino acid [aa] residues 1-604; kindly provided by Dr. Iris Lindberg, University of Maryland Medical School, Baltimore, Md.). F1mutV-PA or PA was treated with different amounts of furin (molar ratio of protein:furin varied from 200,000:1 to 160:1) in 20 μl buffer containing 50 mM HEPES, pH 7.5, 2 mM CaCl2, 0.5 mM EDTA, and 0.2% β-octylglucoside. The reaction was performed at 37° C. for 30 min and terminated by boiling in 2×SDS loading buffer for 5 min. Samples were then analyzed by 4-20% gradient sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDSPAGE).

The binding of F1mutV-PA to the PA receptor CMG2 was carried out by incubation of F1mutV-PA with CMG2 (aa residues 40-218; kindly provided by Dr. Robert Liddington, Sanford-Burnham Medical Research Institute, La Jolla, Calif.) at room temperature for 30 min. F1mutV-PA or PA was incubated with different amounts of CMG2 (molar ratio of protein:CMG2 varied from 4.8:1 to 0.15:1) in 20 μl buffer containing 50 mM HEPES, pH 7.5, 2 mM CaCl2, 0.5 mM EDTA and 0.2% β-octylglucoside. Samples were analyzed by electrophoresis using 4-12% gradient Native-PAGE (Invitrogen).

Binding to the N-terminal domain of lethal factor (LFn) was tested by mixing furin-treated F1mutV-PA with increasing amounts of LFn (molar ratio of F1mutV-PA or PA:LFn varied from 1.92:1 to 0.06:1). F1mutV-PA or PA was cleaved by furin as described above (protein: furin at 160:1) followed by LFn binding for 30 min at room temperature and complex evaluation by electrophoresis using 4-12% gradient Native-PAGE (Invitrogen).

In Vitro Binding of Antigens to T4 Phage Capsid

In vitro binding of Soc fusion protein to Hoc-Soc-T4 phage was carried out as previously described.^(23,25) Briefly, Soc fusion proteins were incubated with the Hoc-Soc-phage at 4° C. for 45 min. The phage particles were centrifuged at 34,000×g for 45 min and the supernatants containing the unbound proteins were discarded. Phage pellets containing the bound plague antigens were washed twice with excess PBS buffer (pH 7.4). The final pellets were resuspended in PBS buffer (pH 7.4) and analyzed by 4-20% gradient SDSPAGE before injection into animals.

Mouse Immunizations and Challenges

Six- to eight-week-old female Balb/c mice (17-20 g) were purchased from The Jackson Laboratory (Bar Harbor, Me.) and randomly grouped and acclimated for 7 days. Phage-displayed antigens were prepared as described above and directly used for immunization without any adjuvant (25 μg each of F1mutV and PA per injection). For other antigens, the purified proteins were adsorbed on Alhydrogel® (Brenntag Biosector, Frederiksund, Denmark) containing 0.19 mg of aluminum per dose. A total of 25 μg antigen was injected for the F1mutV or the PA group, 25 μg F1mutV plus 25 μg PA for the F1mutV+PA group, and 50 μg F1mutV-PA for the F1mutV-PA group on days 0 and 21 via the i.m. route. Control mice received the same amount of Alhydrogel®, but without any antigen. Alternate legs were used for each immunization. Blood was collected from each animal by the retro-orbital route on days 0 (pre-bleeds) and 35. In some studies, mice were i.p. challenged first with 1 LD₁₀₀ of LeTx followed by intranasal challenge with 400 LD₅₀ Y. pestis CO92 33 days after LeTx challenge. In other studies, mice were i.p. challenged with 1 LD₁₀₀ of LeTx and 200 LD₅₀ Y. pestis CO92 on the same day, as indicated in the description for FIGS. 6A through 6C. Animals were monitored twice daily for mortality and other clinical symptoms.

Rat Immunization and Challenge

Female Brown Norway rats (50-75 g), purchased from Charles River Laboratories (New Jersey, N.J.) were randomized into five groups (nine rats per group) and were acclimated for seven days before manipulation. The immunogens were formulated and rats were immunized via i.m. route as described above for mice. Sera were obtained on day 35 for antibody analysis. The animals were bled by the saphenous vein. Rats were first intranasally challenged on day 42 with ˜400 LD₅₀ Y. pestis CO92 and monitored twice daily for morbidity and mortality over a period of 69 days. The animals that survived were further challenged with 1 LD₁₀₀ LeTx (7.5 μg of each of the toxin components [LF and PA], by the i.v. route]) and monitored for another 24 days for morbidity and mortality. In a separate experiment, rats (n=6) were immunized with phage-displayed antigens (25 μg each of F1mutV and PA per injection) or 50 μg F1mutV-PA adsorbed on Alhydrogel® containing 0.19 mg of aluminum on days 0 and 21. One week after last immunization, rats were challenged simultaneously with 1 LD₁₀₀ of LeTx and 400 LD₅₀ Y. pestis CO92 as described above.

Rabbit Immunization and Challenge

Rabbit experiments were performed by Southern Research Institute (Study No: 13538.01.15; Birmingham, Ala.). Briefly, a total of 32 New Zealand white rabbits were divided into four groups. Groups 1 and 2 were vaccinated with T4-F1mutV/PA (25 μg each) and F1mutV-PA (50 μg), respectively (n=10 per group), while group 3 received PA (25 μg; n=6) alone. Alhydrogel® was used as an adjuvant in groups 2 and 3 (600 μg/rabbit). Control animals (group 4) received the same amount of Alhydrogel®, but without any antigen (n=6). Rabbits were injected on day 0 and boosted on day 14. Sera were collected on days 0 (baseline), 12, 20, and 42, and immunological response was monitored by utilizing the anthrax LeTx neutralization assay (TNA) and the enzyme-linked immunosorbent assay (ELISA) with the PA antigen. Anti-F1V IgG was analyzed by utilizing ELISA with the F1V antigen. Animals were challenged with 200 LD₅₀ of aerosolized encapsulated B. anthracis Ames spores on day 28 and monitored for body weight, body temperature, and mortality until day 42 at which point the remaining animals were euthanized. On days 27, 29-33 and 42, blood samples (approximately 0.2 ml) were collected from the central ear artery into tubes containing sodium polyanethole sulfonate and processed for qualitative microbiological analysis (bacteremia) on the same day. On day 42, the remaining animals were euthanized by an intravenous administration of a barbiturate overdose for tissue collection (brain, liver, lung, and spleen). Tissues were further processed for microbiological and histological analyses.

Determination of IgG and IgG Subtype Antibodies

Antibody titers were determined by ELISA as described previously.²³ For rat IgG, horseradish peroxidase (HRP)-conjugated goat anti-rat IgG (KPL, Gaithersburg, Md.) was used as secondary antibodies. For mouse or rat IgG subtypes, HRP-conjugated goat anti-mouse or anti-rat IgG1 or IgG2a secondary antibodies (Abcam, Cambridge, Mass.) were used. For rabbit anti-PA IgG titers, plates were coated with PA and affinity-purified rabbit anti-PA polyclonal antibody was used to generate a standard curve, from which the sample anti-PA IgG concentrations (ng/mL) were determined. Samples were initially at 1:200; additional dilutions were performed as necessary to ensure that values could be determined from the standard curve.

Anthrax LeTx Neutralization Assay (TNA)

Anthrax lethal-toxin-neutralizing assay (TNA) was performed as described previously.⁵⁴ Briefly, PA and LF (200 ng/ml for each component) were prepared in Dulbecco's modified Eagle's medium (DMEM), and sera were diluted serially into the toxin mixture and incubated for 1 h at 37° C. Toxin-serum mixtures were transferred to RAW 264.7 macrophage cells grown to confluence in 96-well plates and incubated for 5 h, and cell viability assessed by incubation with MTT [3-(4,5-dimethylthiazo-2-yl)-2,5-diphenyltetrazolium bromide](Sigma, St. Louis, Mo.) at a final concentration of 0.5 mg/ml for 30 min. An insoluble pigment (formazan) produced by living cells was dissolved in 0.5% (wt/vol) SDS, 25 mM HCl, in 90% (vol/vol) isopropanol, and the optical density (570 nm) measured to assess viability. The effective serum concentration inducing 50% neutralization (EC50) was calculated with Prism software (Graphpad Software, Inc., San Diego, Calif.).

Live Animal Imaging

Depending on the experiment (see figure legends), two or three days after the challenge with Y. pestis CO92-luciferase strain, the animals were imaged by using an IVIS 200 bioluminescence and fluorescence whole-body imaging workstation (Caliper Corp., Alameda, Calif.) in the ABSL-3 facility following light anesthesia under isoflurane.

Statistical Analyses

Results are expressed as mean±standard deviation (SD). Statistical comparisons among different groups were evaluated by analysis of variance (ANOVA). The animal mortality data were analyzed by the Kaplan-Meier survival estimate. A value of p<0.05 was considered statistically significant.

Having described the many embodiments of the disclosed invention in detail, it will be apparent that modifications and variations are possible without departing from the scope of the invention defined in the appended claims. Furthermore, it should be appreciated that all examples in the present disclosure, while illustrating many embodiments of the invention, are provided as non-limiting examples and are, therefore, not to be taken as limiting the various aspects so illustrated.

It is intended that the invention not be limited to the particular embodiment disclosed herein contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims.

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The following references are referred to above and are incorporated herein by reference:

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All documents, patents, journal articles and other materials cited in the present application are incorporated herein by reference.

While the disclosed invention has been disclosed with references to certain embodiments, numerous modification, alterations, and changes to the described embodiments are possible without departing from the sphere and scope of the disclosed invention, as defined in the appended claims. Accordingly, it is intended that the disclosed invention not be limited to the described embodiments, but that it has the full scope defined by the language of the following claims, and equivalents thereof. 

1. An immunogenic composition comprising a triple fusion protein, wherein the triple fusion protein comprises: a mutated F1 antigen from Yersinia pestis, a V antigen from Yersinia pestis, and a protective antigen (PA) from B. anthracis; wherein the mutated F1 antigen, the V antigen, and the PA are fused in-frame; wherein the triple fusion protein has an immunogenicity of the mutated F1 antigen, an immunogenicity of the V antigen, and an immunogenicity of the PA.
 2. The immunogenic composition of claim 1, wherein the mutated F1 antigen is fused in-frame to the N-terminus of the V antigen via a first linker, and wherein the V antigen is fused in-frame to the N-terminus of PA via a second linker.
 3. The immunogenic composition of claim 1, wherein the mutated F1 antigen is modified from a native F1 antigen by deleting N-terminal β-strand residues 1-14 of native F1 antigen, transplanting the N-terminal β-strand residues 1-14 of native F1 antigen to C-terminus, and duplicating residues 15-21 of native F1 antigen at the C-terminus.
 4. The immunogenic composition of claim 1, wherein the mutated F1 antigen comprises a sequence set forth in SEQ ID NO:
 1. 5. The immunogenic composition of claim 1, wherein the triple fusion protein comprises a sequence set forth in SEQ ID NO:
 4. 6. The immunogenic composition of claim 1, wherein the immunogenic composition comprises a pharmaceutically acceptable carrier.
 7. The immunogenic composition of claim 1, wherein the immunogenic composition comprises an adjuvant.
 8. An immunogenic composition comprising one or more bacteriophage nanoparticles arrayed with one or more Soc fusion proteins on capsid surface of each bacteriophage nanoparticle, wherein the one or more Soc fusion proteins comprises a Soc fused to an antigen selected from the group consisting of a mutated F1 antigen from Yersinia pestis, a V antigen from Yersinia pestis, a protective antigen (PA) from B. anthracis, and combination thereof. 9-20. (canceled) 